diff --git a/src/parser/flow_ast_utils.ml b/src/parser/flow_ast_utils.ml
index 5322d519ed2..030e6f70f1e 100644
--- a/src/parser/flow_ast_utils.ml
+++ b/src/parser/flow_ast_utils.ml
@@ -215,56 +215,60 @@ let is_super_member_access = function
   | { Flow_ast.Expression.Member._object = (_, Flow_ast.Expression.Super _); _ } -> true
   | _ -> false
 
-let acceptable_statement_in_declaration_context ~in_declare_namespace = function
-  | Flow_ast.Statement.Block _ -> Error "block"
-  | Flow_ast.Statement.Break _ -> Error "break"
-  | Flow_ast.Statement.ClassDeclaration _ -> Error "class declaration"
-  | Flow_ast.Statement.ComponentDeclaration _ -> Error "component declaration"
-  | Flow_ast.Statement.Continue _ -> Error "continue"
-  | Flow_ast.Statement.Debugger _ -> Error "debugger"
-  | Flow_ast.Statement.DoWhile _ -> Error "do while"
-  | Flow_ast.Statement.ExportDefaultDeclaration _ -> Error "export"
-  | Flow_ast.Statement.ExportNamedDeclaration _ -> Error "export"
-  | Flow_ast.Statement.Expression _ -> Error "expression"
-  | Flow_ast.Statement.For _ -> Error "for"
-  | Flow_ast.Statement.ForIn _ -> Error "for in"
-  | Flow_ast.Statement.ForOf _ -> Error "for of"
-  | Flow_ast.Statement.FunctionDeclaration _ -> Error "function declaration"
-  | Flow_ast.Statement.If _ -> Error "if"
-  | Flow_ast.Statement.Labeled _ -> Error "labeled"
-  | Flow_ast.Statement.Return _ -> Error "return"
-  | Flow_ast.Statement.Switch _ -> Error "switch"
-  | Flow_ast.Statement.Throw _ -> Error "throw"
-  | Flow_ast.Statement.Try _ -> Error "try"
-  | Flow_ast.Statement.VariableDeclaration _ -> Error "variable declaration"
-  | Flow_ast.Statement.While _ -> Error "while"
-  | Flow_ast.Statement.With _ -> Error "with"
-  | Flow_ast.Statement.ImportDeclaration _ ->
+let acceptable_statement_in_declaration_context ~in_declare_namespace =
+  let open Flow_ast.Statement in
+  function
+  | Block _ -> Error "block"
+  | Break _ -> Error "break"
+  | ClassDeclaration _ -> Error "class declaration"
+  | ComponentDeclaration _ -> Error "component declaration"
+  | Continue _ -> Error "continue"
+  | Debugger _ -> Error "debugger"
+  | DoWhile _ -> Error "do while"
+  | ExportDefaultDeclaration _ -> Error "export default"
+  | ExportNamedDeclaration { ExportNamedDeclaration.export_kind = ExportValue; _ } ->
+    Error "value export"
+  | Expression _ -> Error "expression"
+  | For _ -> Error "for"
+  | ForIn _ -> Error "for in"
+  | ForOf _ -> Error "for of"
+  | FunctionDeclaration _ -> Error "function declaration"
+  | If _ -> Error "if"
+  | Labeled _ -> Error "labeled"
+  | Return _ -> Error "return"
+  | Switch _ -> Error "switch"
+  | Throw _ -> Error "throw"
+  | Try _ -> Error "try"
+  | VariableDeclaration _ -> Error "variable declaration"
+  | While _ -> Error "while"
+  | With _ -> Error "with"
+  | ImportDeclaration _ ->
     if in_declare_namespace then
       Error "import declaration"
     else
       Ok ()
-  | Flow_ast.Statement.DeclareModuleExports _ ->
+  | DeclareModuleExports _ ->
     if in_declare_namespace then
       Error "declare module.exports"
     else
       Ok ()
-  | Flow_ast.Statement.DeclareClass _
-  | Flow_ast.Statement.DeclareComponent _
-  | Flow_ast.Statement.DeclareEnum _
-  | Flow_ast.Statement.DeclareExportDeclaration _
-  | Flow_ast.Statement.DeclareFunction _
-  | Flow_ast.Statement.DeclareInterface _
-  | Flow_ast.Statement.DeclareModule _
-  | Flow_ast.Statement.DeclareNamespace _
-  | Flow_ast.Statement.DeclareOpaqueType _
-  | Flow_ast.Statement.DeclareTypeAlias _
-  | Flow_ast.Statement.DeclareVariable _
-  | Flow_ast.Statement.Empty _
-  | Flow_ast.Statement.EnumDeclaration _
-  | Flow_ast.Statement.InterfaceDeclaration _
-  | Flow_ast.Statement.OpaqueType _
-  | Flow_ast.Statement.TypeAlias _ ->
+  | DeclareClass _
+  | DeclareComponent _
+  | DeclareEnum _
+  | DeclareExportDeclaration _
+  | DeclareFunction _
+  | DeclareInterface _
+  | DeclareModule _
+  | DeclareNamespace _
+  | DeclareOpaqueType _
+  | DeclareTypeAlias _
+  | DeclareVariable _
+  | Empty _
+  | EnumDeclaration _
+  | ExportNamedDeclaration { ExportNamedDeclaration.export_kind = ExportType; _ }
+  | InterfaceDeclaration _
+  | OpaqueType _
+  | TypeAlias _ ->
     Ok ()
 
 let rec is_type_only_declaration_statement (_, stmt') =
@@ -284,6 +288,7 @@ let rec is_type_only_declaration_statement (_, stmt') =
       true
     | DeclareNamespace { DeclareNamespace.body = (_, { Block.body; _ }); _ } ->
       List.for_all is_type_only_declaration_statement body
+    | ExportNamedDeclaration { ExportNamedDeclaration.export_kind; _ } -> export_kind = ExportType
     | Block _
     | Break _
     | ClassDeclaration _
@@ -293,7 +298,6 @@ let rec is_type_only_declaration_statement (_, stmt') =
     | DoWhile _
     | EnumDeclaration _
     | ExportDefaultDeclaration _
-    | ExportNamedDeclaration _
     | Expression _
     | For _
     | ForIn _
diff --git a/src/parser_utils/type_sig/__tests__/type_sig_tests.ml b/src/parser_utils/type_sig/__tests__/type_sig_tests.ml
index 19152b8a347..1aed3ff101c 100644
--- a/src/parser_utils/type_sig/__tests__/type_sig_tests.ml
+++ b/src/parser_utils/type_sig/__tests__/type_sig_tests.ml
@@ -5566,19 +5566,25 @@ let%expect_test "builtin_cjs_module_auto_export_type" =
   (* All types in cjs modules are auto exported. *)
   print_builtins [{|
     declare module foo {
-      declare type T = number;
+      declare type T1 = number;
+      export type T2 = string;
       declare module.exports: string;
     }
   |}];
   [%expect {|
     Local defs:
-    0. TypeAlias {id_loc = [2:15-16]; name = "T"; tparams = Mono; body = (Annot (Number [2:19-25]))}
+    0. TypeAlias {id_loc = [2:15-17];
+         name = "T1"; tparams = Mono;
+         body = (Annot (Number [2:20-26]))}
+    1. TypeAlias {id_loc = [3:14-16];
+         name = "T2"; tparams = Mono;
+         body = (Annot (String [3:19-25]))}
 
     Builtin module foo:
-    [1:15-18] CJSModule {type_exports = [|(ExportTypeBinding 0)|];
-                exports = (Some (Annot (String [3:26-32])));
+    [1:15-18] CJSModule {type_exports = [|(ExportTypeBinding 0); (ExportTypeBinding 1)|];
+                exports = (Some (Annot (String [4:26-32])));
                 info =
-                CJSModuleInfo {type_export_keys = [|"T"|];
+                CJSModuleInfo {type_export_keys = [|"T1"; "T2"|];
                   type_stars = []; strict = true;
                   platform_availability_set = None}} |}]
 
@@ -5667,6 +5673,7 @@ let%expect_test "builtin_cjs_module_with_implicit_exports" =
       declare enum A { B }
       declare type T = number;
       declare export type U = string;
+      export const ignored = 3; // unsupported;
     }
   |}];
   [%expect {|
@@ -5881,11 +5888,14 @@ let%expect_test "builtin_declare_namespace" =
       declare function f(): string;
       declare function f(): number;
       declare type Baz = string;
+      export type Boz = string;
       enum B {
         C,
         D,
       }
       if (true) {} // unsupported
+      export const foo = ''; // unsupported
+      export default foo; // unsupported
       declare module.exports: {foo: string}; // unsupported
       import React from 'react'; // unsupported
     }
@@ -5912,19 +5922,24 @@ let%expect_test "builtin_declare_namespace" =
     4. TypeAlias {id_loc = [7:15-18];
          name = "Baz"; tparams = Mono;
          body = (Annot (String [7:21-27]))}
-    5. EnumBinding {id_loc = [8:7-8];
+    5. TypeAlias {id_loc = [8:14-17];
+         name = "Boz"; tparams = Mono;
+         body = (Annot (String [8:20-26]))}
+    6. EnumBinding {id_loc = [9:7-8];
          name = "B"; rep = StringRep {truthy = true};
-         members = { "C" -> [9:4-5]; "D" -> [10:4-5] };
+         members = { "C" -> [10:4-5]; "D" -> [11:4-5] };
          has_unknown_members = false}
-    6. NamespaceBinding {id_loc = [1:18-20];
+    7. NamespaceBinding {id_loc = [1:18-20];
          name = "ns";
          values =
-         { "B" -> ([8:7-8], (Ref LocalRef {ref_loc = [8:7-8]; index = 5}));
+         { "B" -> ([9:7-8], (Ref LocalRef {ref_loc = [9:7-8]; index = 6}));
            "bar1" -> ([2:23-27], (Ref LocalRef {ref_loc = [2:23-27]; index = 0}));
            "bar2" -> ([3:16-20], (Ref LocalRef {ref_loc = [3:16-20]; index = 1}));
            "bar3" -> ([4:14-18], (Ref LocalRef {ref_loc = [4:14-18]; index = 2}));
            "f" -> ([5:19-20], (Ref LocalRef {ref_loc = [5:19-20]; index = 3})) };
-         types = { "Baz" -> ([7:15-18], (Ref LocalRef {ref_loc = [7:15-18]; index = 4})) }}
+         types =
+         { "Baz" -> ([7:15-18], (Ref LocalRef {ref_loc = [7:15-18]; index = 4}));
+           "Boz" -> ([8:14-17], (Ref LocalRef {ref_loc = [8:14-17]; index = 5})) }}
 
     Builtin global value ns |}]
 
diff --git a/src/typing/errors/error_message.ml b/src/typing/errors/error_message.ml
index e2a68de44c0..6b83848ab96 100644
--- a/src/typing/errors/error_message.ml
+++ b/src/typing/errors/error_message.ml
@@ -3182,14 +3182,14 @@ let friendly_message_of_msg loc_of_aloc msg =
       | ContextDependentUnsupportedStatement (UnsupportedStatementInLibdef kind) ->
         [
           text "Cannot use ";
-          code kind;
+          text kind;
           text " statements in a library file. ";
           text "The statement will be ignored.";
         ]
       | ContextDependentUnsupportedStatement (UnsupportedStatementInDeclareModule kind) ->
         [
           text "Cannot use ";
-          code kind;
+          text kind;
           text " statements with in ";
           code "declare module";
           text ". The statement will be ignored.";
@@ -3197,7 +3197,7 @@ let friendly_message_of_msg loc_of_aloc msg =
       | ContextDependentUnsupportedStatement (UnsupportedStatementInDeclareNamespace kind) ->
         [
           text "Cannot use ";
-          code kind;
+          text kind;
           text " statements with in ";
           code "declare namespace";
           text ". The statement will be ignored.";
diff --git a/src/typing/type_inference_js.ml b/src/typing/type_inference_js.ml
index ee0f6458124..cfc4afd0bfc 100644
--- a/src/typing/type_inference_js.ml
+++ b/src/typing/type_inference_js.ml
@@ -433,7 +433,7 @@ class lib_def_loc_mapper_and_validator cx =
       | OpaqueType _ ->
         None
       | ExportNamedDeclaration { ExportNamedDeclaration.export_kind = ExportValue; _ } ->
-        Some (error "export")
+        Some (error "value export")
       | ImportDeclaration _ ->
         if in_toplevel_scope then
           Some
diff --git a/tests/declare_namespace/declare_namespace.exp b/tests/declare_namespace/declare_namespace.exp
index 0443d8fa4c8..ea94d8a930d 100644
--- a/tests/declare_namespace/declare_namespace.exp
+++ b/tests/declare_namespace/declare_namespace.exp
@@ -71,159 +71,204 @@ References:
 
 Error -------------------------------------------------------------------------------------------------- exported.js:9:3
 
-Cannot use `if` statements with in `declare namespace`. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements with in `declare namespace`. The statement will be ignored. [unsupported-syntax]
 
    9|   if (true) {} // unsupported
         ^^^^^^^^^^^^
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:10:3
+Error ------------------------------------------------------------------------------------------------- exported.js:12:3
 
-Cannot use `declare module.exports` statements with in `declare namespace`. The statement will be ignored.
+Cannot use value export statements with in `declare namespace`. The statement will be ignored. [unsupported-syntax]
+
+   12|   export const CONSTANT = 'foo'; // unsupported
+         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------------------------- exported.js:13:3
+
+Cannot use export default statements with in `declare namespace`. The statement will be ignored. [unsupported-syntax]
+
+   13|   export default CONSTANT; // unsupported
+         ^^^^^^^^^^^^^^^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------------------------- exported.js:14:3
+
+Cannot use declare module.exports statements with in `declare namespace`. The statement will be ignored.
 [unsupported-syntax]
 
-   10|   declare module.exports: {foo: string}; // unsupported
+   14|   declare module.exports: {foo: string}; // unsupported
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:10:3
+Error ------------------------------------------------------------------------------------------------- exported.js:14:3
 
 Unable to determine module type (CommonJS vs ES) if both an export statement and `module.exports` are used in the same
 module! [module-type-conflict]
 
-   10|   declare module.exports: {foo: string}; // unsupported
+   14|   declare module.exports: {foo: string}; // unsupported
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:11:3
+Error ------------------------------------------------------------------------------------------------- exported.js:15:3
 
-Cannot use `import declaration` statements with in `declare namespace`. The statement will be ignored.
+Cannot use import declaration statements with in `declare namespace`. The statement will be ignored.
 [unsupported-syntax]
 
-   11|   import React from 'react'; // unsupported
+   15|   import React from 'react'; // unsupported
          ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:22:3
+Error ------------------------------------------------------------------------------------------------- exported.js:26:3
 
 Cannot use type-only namespace `empty` [1] as a value. Type-only namespaces are erased and don't exist at runtime.
 [type-as-value]
 
-   exported.js:22:3
-   22|   empty, // error: empty is type-only
+   exported.js:26:3
+   26|   empty, // error: empty is type-only
          ^^^^^
 
 References:
-   exported.js:14:19
-   14| declare namespace empty {}
+   exported.js:18:19
+   18| declare namespace empty {}
                          ^^^^^ [1]
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:27:1
+Error ------------------------------------------------------------------------------------------------- exported.js:31:1
 
 Cannot cast `exported_ns.bar1` to empty because number [1] is incompatible with empty [2]. [incompatible-cast]
 
-   exported.js:27:1
-   27| exported_ns.bar1 as empty; // error: number ~> empty
+   exported.js:31:1
+   31| exported_ns.bar1 as empty; // error: number ~> empty
        ^^^^^^^^^^^^^^^^
 
 References:
    exported.js:2:30
     2|   declare export const bar1: number;
                                     ^^^^^^ [1]
-   exported.js:27:21
-   27| exported_ns.bar1 as empty; // error: number ~> empty
+   exported.js:31:21
+   31| exported_ns.bar1 as empty; // error: number ~> empty
                            ^^^^^ [2]
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:28:1
+Error ------------------------------------------------------------------------------------------------- exported.js:32:1
 
 Cannot cast `exported_ns.bar2` to empty because boolean [1] is incompatible with empty [2]. [incompatible-cast]
 
-   exported.js:28:1
-   28| exported_ns.bar2 as empty; // error: boolean ~> empty
+   exported.js:32:1
+   32| exported_ns.bar2 as empty; // error: boolean ~> empty
        ^^^^^^^^^^^^^^^^
 
 References:
    exported.js:3:23
     3|   declare const bar2: boolean;
                              ^^^^^^^ [1]
-   exported.js:28:21
-   28| exported_ns.bar2 as empty; // error: boolean ~> empty
+   exported.js:32:21
+   32| exported_ns.bar2 as empty; // error: boolean ~> empty
                            ^^^^^ [2]
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:29:1
+Error ------------------------------------------------------------------------------------------------- exported.js:33:1
 
 Cannot cast `exported_ns.bar3` to empty because string [1] is incompatible with empty [2]. [incompatible-cast]
 
-   exported.js:29:1
-   29| exported_ns.bar3 as empty; // error: string ~> empty
+   exported.js:33:1
+   33| exported_ns.bar3 as empty; // error: string ~> empty
        ^^^^^^^^^^^^^^^^
 
 References:
    exported.js:4:21
     4|   declare var bar3: string;
                            ^^^^^^ [1]
-   exported.js:29:21
-   29| exported_ns.bar3 as empty; // error: string ~> empty
+   exported.js:33:21
+   33| exported_ns.bar3 as empty; // error: string ~> empty
                            ^^^^^ [2]
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:30:1
+Error ------------------------------------------------------------------------------------------------- exported.js:34:1
 
 Cannot cast `exported_ns.f(...)` to empty because number [1] is incompatible with empty [2]. [incompatible-cast]
 
-   exported.js:30:1
-   30| exported_ns.f(3) as empty; // error: number ~> empty
+   exported.js:34:1
+   34| exported_ns.f(3) as empty; // error: number ~> empty
        ^^^^^^^^^^^^^^^^
 
 References:
    exported.js:6:31
     6|   declare function f(number): number;
                                      ^^^^^^ [1]
-   exported.js:30:21
-   30| exported_ns.f(3) as empty; // error: number ~> empty
+   exported.js:34:21
+   34| exported_ns.f(3) as empty; // error: number ~> empty
                            ^^^^^ [2]
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:31:1
+Error ------------------------------------------------------------------------------------------------- exported.js:35:1
 
 Cannot cast `1` to `Baz` because number [1] is incompatible with string [2]. [incompatible-cast]
 
-   exported.js:31:1
-   31| 1 as exported_ns.Baz; // error: number ~> string
+   exported.js:35:1
+   35| 1 as exported_ns.Baz; // error: number ~> string
        ^ [1]
 
 References:
-   exported.js:31:6
-   31| 1 as exported_ns.Baz; // error: number ~> string
+   exported.js:35:6
+   35| 1 as exported_ns.Baz; // error: number ~> string
             ^^^^^^^^^^^^^^^ [2]
 
 
-Error ------------------------------------------------------------------------------------------------- exported.js:32:1
+Error ------------------------------------------------------------------------------------------------- exported.js:36:1
+
+Cannot cast `1` to `Baz2` because number [1] is incompatible with string [2]. [incompatible-cast]
+
+   exported.js:36:1
+   36| 1 as exported_ns.Baz2; // error: number ~> string
+       ^ [1]
+
+References:
+   exported.js:36:6
+   36| 1 as exported_ns.Baz2; // error: number ~> string
+            ^^^^^^^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------- exported.js:37:1
+
+Cannot cast `1` to `Baz3` because number [1], a primitive, cannot be used as a subtype of `Baz3` [2]. You can wrap it in
+`new Number(...))` to turn it into an object and attempt to use it as a subtype of an interface. [incompatible-type]
+
+   exported.js:37:1
+   37| 1 as exported_ns.Baz3; // error: number ~> interface {}
+       ^ [1]
+
+References:
+   exported.js:37:6
+   37| 1 as exported_ns.Baz3; // error: number ~> interface {}
+            ^^^^^^^^^^^^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------- exported.js:38:1
 
 Cannot cast `exported_ns.B.C` to empty because `B` [1] is incompatible with empty [2]. [incompatible-cast]
 
-   exported.js:32:1
-   32| exported_ns.B.C as empty; // error: enum ~> empty
+   exported.js:38:1
+   38| exported_ns.B.C as empty; // error: enum ~> empty
        ^^^^^^^^^^^^^^^
 
 References:
    exported.js:8:8
     8|   enum B { C, D }
               ^ [1]
-   exported.js:32:20
-   32| exported_ns.B.C as empty; // error: enum ~> empty
+   exported.js:38:20
+   38| exported_ns.B.C as empty; // error: enum ~> empty
                           ^^^^^ [2]
 
 
-Error ------------------------------------------------------------------------------------------------ exported.js:33:13
+Error ------------------------------------------------------------------------------------------------ exported.js:39:13
 
 Cannot get `exported_ns.React` because property `React` is missing in namespace exported_ns [1]. [prop-missing]
 
-   exported.js:33:13
-   33| exported_ns.React; // error: prop-missing
+   exported.js:39:13
+   39| exported_ns.React; // error: prop-missing
                    ^^^^^
 
 References:
@@ -232,6 +277,35 @@ References:
                          ^^^^^^^^^^^ [1]
 
 
+Error ------------------------------------------------------------------------------------------------- exported.js:40:1
+
+Cannot cast `exported_ns.CONSTANT` to empty because `void` (due to access of non-existent property `CONSTANT`) [1] is
+incompatible with empty [2]. [incompatible-cast]
+
+   exported.js:40:1
+   40| exported_ns.CONSTANT as empty; // prop-missing
+       ^^^^^^^^^^^^^^^^^^^^ [1]
+
+References:
+   exported.js:40:25
+   40| exported_ns.CONSTANT as empty; // prop-missing
+                               ^^^^^ [2]
+
+
+Error ------------------------------------------------------------------------------------------------ exported.js:40:13
+
+Cannot get `exported_ns.CONSTANT` because property `CONSTANT` is missing in namespace exported_ns [1]. [prop-missing]
+
+   exported.js:40:13
+   40| exported_ns.CONSTANT as empty; // prop-missing
+                   ^^^^^^^^
+
+References:
+   exported.js:1:19
+    1| declare namespace exported_ns {
+                         ^^^^^^^^^^^ [1]
+
+
 Error --------------------------------------------------------------------------------- type_only_react_namespace.js:3:3
 
 Cannot resolve name `React`. [cannot-resolve-name]
@@ -339,7 +413,7 @@ use it as an annotation. [value-as-type]
 
 Error ---------------------------------------------------------------------------------------------- typing_test.js:12:3
 
-Cannot use `declare module.exports` statements with in `declare namespace`. The statement will be ignored.
+Cannot use declare module.exports statements with in `declare namespace`. The statement will be ignored.
 [unsupported-syntax]
 
    12|   declare module.exports: {foo: string}; // unsupported
@@ -363,7 +437,7 @@ References:
 
 Error ---------------------------------------------------------------------------------------------- typing_test.js:23:3
 
-Cannot use `if` statements with in `declare namespace`. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements with in `declare namespace`. The statement will be ignored. [unsupported-syntax]
 
    23|   if (true) {} // error
          ^^^^^^^^^^^^
@@ -371,7 +445,7 @@ Cannot use `if` statements with in `declare namespace`. The statement will be ig
 
 Error ---------------------------------------------------------------------------------------------- typing_test.js:24:3
 
-Cannot use `import declaration` statements with in `declare namespace`. The statement will be ignored.
+Cannot use import declaration statements with in `declare namespace`. The statement will be ignored.
 [unsupported-syntax]
 
    24|   import React from 'react'; // unsupported
@@ -496,27 +570,56 @@ References:
 
 Error ---------------------------------------------------------------------------------------------- typing_test.js:36:1
 
-Cannot cast `exported_ns.B.C` to empty because `B` [1] is incompatible with empty [2]. [incompatible-cast]
+Cannot cast `1` to `Baz2` because number [1] is incompatible with string [2]. [incompatible-cast]
 
    typing_test.js:36:1
-   36| exported_ns.B.C as empty; // error: enum ~> empty
+   36| 1 as exported_ns.Baz2; // error: number ~> string
+       ^ [1]
+
+References:
+   typing_test.js:36:6
+   36| 1 as exported_ns.Baz2; // error: number ~> string
+            ^^^^^^^^^^^^^^^^ [2]
+
+
+Error ---------------------------------------------------------------------------------------------- typing_test.js:37:1
+
+Cannot cast `1` to `Baz3` because number [1], a primitive, cannot be used as a subtype of `Baz3` [2]. You can wrap it in
+`new Number(...))` to turn it into an object and attempt to use it as a subtype of an interface. [incompatible-type]
+
+   typing_test.js:37:1
+   37| 1 as exported_ns.Baz3; // error: number ~> interface {}
+       ^ [1]
+
+References:
+   typing_test.js:37:6
+   37| 1 as exported_ns.Baz3; // error: number ~> interface {}
+            ^^^^^^^^^^^^^^^^ [2]
+
+
+Error ---------------------------------------------------------------------------------------------- typing_test.js:38:1
+
+Cannot cast `exported_ns.B.C` to empty because `B` [1] is incompatible with empty [2]. [incompatible-cast]
+
+   typing_test.js:38:1
+   38| exported_ns.B.C as empty; // error: enum ~> empty
        ^^^^^^^^^^^^^^^
 
 References:
    exported.js:8:8
     8|   enum B { C, D }
               ^ [1]
-   typing_test.js:36:20
-   36| exported_ns.B.C as empty; // error: enum ~> empty
+   typing_test.js:38:20
+   38| exported_ns.B.C as empty; // error: enum ~> empty
                           ^^^^^ [2]
 
 
-Error --------------------------------------------------------------------------------------------- typing_test.js:37:13
+Error --------------------------------------------------------------------------------------------- typing_test.js:39:13
 
 Cannot get `exported_ns.React` because property `React` is missing in namespace exported_ns [1]. [prop-missing]
 
-   typing_test.js:37:13
-   37| exported_ns.React; // error: prop-missing
+   typing_test.js:39:13
+   39| exported_ns.React; // error: prop-missing
                    ^^^^^
 
 References:
@@ -525,102 +628,131 @@ References:
                          ^^^^^^^^^^^ [1]
 
 
-Error ---------------------------------------------------------------------------------------------- typing_test.js:41:1
+Error ---------------------------------------------------------------------------------------------- typing_test.js:40:1
+
+Cannot cast `exported_ns.CONSTANT` to empty because `void` (due to access of non-existent property `CONSTANT`) [1] is
+incompatible with empty [2]. [incompatible-cast]
+
+   typing_test.js:40:1
+   40| exported_ns.CONSTANT as empty; // error: prop-missing
+       ^^^^^^^^^^^^^^^^^^^^ [1]
+
+References:
+   typing_test.js:40:25
+   40| exported_ns.CONSTANT as empty; // error: prop-missing
+                               ^^^^^ [2]
+
+
+Error --------------------------------------------------------------------------------------------- typing_test.js:40:13
+
+Cannot get `exported_ns.CONSTANT` because property `CONSTANT` is missing in namespace exported_ns [1]. [prop-missing]
+
+   typing_test.js:40:13
+   40| exported_ns.CONSTANT as empty; // error: prop-missing
+                   ^^^^^^^^
+
+References:
+   exported.js:1:19
+    1| declare namespace exported_ns {
+                         ^^^^^^^^^^^ [1]
+
+
+Error ---------------------------------------------------------------------------------------------- typing_test.js:44:1
 
 Cannot use type `exported_ns_type_only` [1] as a value. Types are erased and don't exist at runtime. If the exported
 binding can also be used as a value, try importing it using `import exported_ns_type_only` instead of
 `import type exported_ns_type_only` and `import {exported_ns_type_only}` instead of
 `import type {exported_ns_type_only}`. [type-as-value]
 
-   typing_test.js:41:1
-   41| exported_ns_type_only; exported_ns_type_only2; // error: type-as-value
+   typing_test.js:44:1
+   44| exported_ns_type_only; exported_ns_type_only2; // error: type-as-value
        ^^^^^^^^^^^^^^^^^^^^^
 
 References:
-   typing_test.js:40:51
-   40| import type {type_only as exported_ns_type_only2, exported_ns_type_only} from './exported';
+   typing_test.js:43:51
+   43| import type {type_only as exported_ns_type_only2, exported_ns_type_only} from './exported';
                                                          ^^^^^^^^^^^^^^^^^^^^^ [1]
 
 
-Error --------------------------------------------------------------------------------------------- typing_test.js:41:24
+Error --------------------------------------------------------------------------------------------- typing_test.js:44:24
 
 Cannot use type `exported_ns_type_only2` [1] as a value. Types are erased and don't exist at runtime. If the exported
 binding can also be used as a value, try importing it using `import exported_ns_type_only2` instead of
 `import type exported_ns_type_only2` and `import {exported_ns_type_only2}` instead of
 `import type {exported_ns_type_only2}`. [type-as-value]
 
-   typing_test.js:41:24
-   41| exported_ns_type_only; exported_ns_type_only2; // error: type-as-value
+   typing_test.js:44:24
+   44| exported_ns_type_only; exported_ns_type_only2; // error: type-as-value
                               ^^^^^^^^^^^^^^^^^^^^^^
 
 References:
-   typing_test.js:40:27
-   40| import type {type_only as exported_ns_type_only2, exported_ns_type_only} from './exported';
+   typing_test.js:43:27
+   43| import type {type_only as exported_ns_type_only2, exported_ns_type_only} from './exported';
                                  ^^^^^^^^^^^^^^^^^^^^^^ [1]
 
 
-Error ---------------------------------------------------------------------------------------------- typing_test.js:45:3
+Error ---------------------------------------------------------------------------------------------- typing_test.js:48:3
 
 Cannot cast `1` to `B` because number [1] is incompatible with `B` [2]. [incompatible-cast]
 
-   typing_test.js:45:3
-   45|   1 as exported_ns_type_only.B; // error: number ~> enum
+   typing_test.js:48:3
+   48|   1 as exported_ns_type_only.B; // error: number ~> enum
          ^ [1]
 
 References:
-   typing_test.js:45:8
-   45|   1 as exported_ns_type_only.B; // error: number ~> enum
+   typing_test.js:48:8
+   48|   1 as exported_ns_type_only.B; // error: number ~> enum
               ^^^^^^^^^^^^^^^^^^^^^^^ [2]
 
 
-Error ---------------------------------------------------------------------------------------------- typing_test.js:47:3
+Error ---------------------------------------------------------------------------------------------- typing_test.js:50:3
 
 Cannot cast `exported_ns.B.C` to `T` because `B` [1] is incompatible with number [2]. [incompatible-cast]
 
-   typing_test.js:47:3
-   47|   exported_ns.B.C as exported_ns_type_only2.T; // error: enum ~> number
+   typing_test.js:50:3
+   50|   exported_ns.B.C as exported_ns_type_only2.T; // error: enum ~> number
          ^^^^^^^^^^^^^^^
 
 References:
    exported.js:8:8
     8|   enum B { C, D }
               ^ [1]
-   typing_test.js:47:22
-   47|   exported_ns.B.C as exported_ns_type_only2.T; // error: enum ~> number
+   typing_test.js:50:22
+   50|   exported_ns.B.C as exported_ns_type_only2.T; // error: enum ~> number
                             ^^^^^^^^^^^^^^^^^^^^^^^^ [2]
 
 
-Error ---------------------------------------------------------------------------------------------- typing_test.js:52:3
+Error ---------------------------------------------------------------------------------------------- typing_test.js:55:3
 
 Cannot use type-only namespace `type_only` [1] as a value. Type-only namespaces are erased and don't exist at runtime.
 [type-as-value]
 
-   typing_test.js:52:3
-   52|   type_only; // error: type-as-value
+   typing_test.js:55:3
+   55|   type_only; // error: type-as-value
          ^^^^^^^^^
 
 References:
-   typing_test.js:49:21
-   49|   declare namespace type_only {
+   typing_test.js:52:21
+   52|   declare namespace type_only {
                            ^^^^^^^^^ [1]
 
 
-Error ---------------------------------------------------------------------------------------------- typing_test.js:54:3
+Error ---------------------------------------------------------------------------------------------- typing_test.js:57:3
 
 Cannot cast `1` to `Bar` because number [1] is incompatible with string [2]. [incompatible-cast]
 
-   typing_test.js:54:3
-   54|   1 as type_only.Bar; // error: number ~> string
+   typing_test.js:57:3
+   57|   1 as type_only.Bar; // error: number ~> string
          ^ [1]
 
 References:
-   typing_test.js:54:8
-   54|   1 as type_only.Bar; // error: number ~> string
+   typing_test.js:57:8
+   57|   1 as type_only.Bar; // error: number ~> string
               ^^^^^^^^^^^^^ [2]
 
 
 
-Found 43 errors
+Found 53 errors
 
 Only showing the most relevant union/intersection branches.
 To see all branches, re-run Flow with --show-all-branches
diff --git a/tests/declare_namespace/exported.js b/tests/declare_namespace/exported.js
index 5dd1446eb8e..61e4e7e8b13 100644
--- a/tests/declare_namespace/exported.js
+++ b/tests/declare_namespace/exported.js
@@ -7,6 +7,10 @@ declare namespace exported_ns {
   declare type Baz = string;
   enum B { C, D }
   if (true) {} // unsupported
+  export type Baz2 = string;
+  export interface Baz3 {}
+  export const CONSTANT = 'foo'; // unsupported
+  export default CONSTANT; // unsupported
   declare module.exports: {foo: string}; // unsupported
   import React from 'react'; // unsupported
 }
@@ -29,5 +33,8 @@ exported_ns.bar2 as empty; // error: boolean ~> empty
 exported_ns.bar3 as empty; // error: string ~> empty
 exported_ns.f(3) as empty; // error: number ~> empty
 1 as exported_ns.Baz; // error: number ~> string
+1 as exported_ns.Baz2; // error: number ~> string
+1 as exported_ns.Baz3; // error: number ~> interface {}
 exported_ns.B.C as empty; // error: enum ~> empty
 exported_ns.React; // error: prop-missing
+exported_ns.CONSTANT as empty; // prop-missing
diff --git a/tests/declare_namespace/typing_test.js b/tests/declare_namespace/typing_test.js
index e6885c6564a..9d8525f4376 100644
--- a/tests/declare_namespace/typing_test.js
+++ b/tests/declare_namespace/typing_test.js
@@ -33,8 +33,11 @@ exported_ns.bar2 as empty; // error: boolean ~> empty
 exported_ns.bar3 as empty; // error: string ~> empty
 exported_ns.f(3) as empty; // error: number ~> empty
 1 as exported_ns.Baz; // error: number ~> string
+1 as exported_ns.Baz2; // error: number ~> string
+1 as exported_ns.Baz3; // error: number ~> interface {}
 exported_ns.B.C as empty; // error: enum ~> empty
 exported_ns.React; // error: prop-missing
+exported_ns.CONSTANT as empty; // error: prop-missing
 empty as empty; // ok: already errored being type-only in exported.js
 
 import type {type_only as exported_ns_type_only2, exported_ns_type_only} from './exported';
diff --git a/tests/liberr/liberr.exp b/tests/liberr/liberr.exp
index 1cbd437a24b..c76658c1b17 100644
--- a/tests/liberr/liberr.exp
+++ b/tests/liberr/liberr.exp
@@ -55,7 +55,7 @@ Error --------------------------------------------------------------------------
 
 Error --------------------------------------------------------------------------------------- libs/invalid-nested.js:5:1
 
-Cannot use `block` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use block statements in a library file. The statement will be ignored. [unsupported-syntax]
 
       v
    5| {
@@ -66,7 +66,7 @@ Cannot use `block` statements in a library file. The statement will be ignored.
 
 Error --------------------------------------------------------------------------------------- libs/invalid-nested.js:9:1
 
-Cannot use `if` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements in a library file. The statement will be ignored. [unsupported-syntax]
 
        v----------
     9| if (true) {
@@ -101,7 +101,7 @@ Cannot use type without exactly 1 type argument. [nonpolymorphic-type-app]
 
 Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:3:3
 
-Cannot use `if` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements in a library file. The statement will be ignored. [unsupported-syntax]
 
    3|   if (true) {} // error
         ^^^^^^^^^^^^
@@ -109,12 +109,28 @@ Cannot use `if` statements in a library file. The statement will be ignored. [un
 
 Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:3:3
 
-Cannot use `if` statements with in `declare module`. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements with in `declare module`. The statement will be ignored. [unsupported-syntax]
 
    3|   if (true) {} // error
         ^^^^^^^^^^^^
 
 
+Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:4:3
+
+Cannot use value export statements in a library file. The statement will be ignored. [unsupported-syntax]
+
+   4|   export const foo = ''; // error
+        ^^^^^^^^^^^^^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:4:3
+
+Cannot use value export statements with in `declare module`. The statement will be ignored. [unsupported-syntax]
+
+   4|   export const foo = ''; // error
+        ^^^^^^^^^^^^^^^^^^^^^^
+
+
 Error -------------------------------------------------------------------------------------------------------- a.js:5:17
 
 Cannot assign `0` to `x` because number [1] is incompatible with string [2]. [incompatible-type]
@@ -205,7 +221,7 @@ References:
 
 
 
-Found 20 errors
+Found 22 errors
 
 ============================================
 With warnings:
@@ -264,7 +280,7 @@ Error --------------------------------------------------------------------------
 
 Error --------------------------------------------------------------------------------------- libs/invalid-nested.js:5:1
 
-Cannot use `block` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use block statements in a library file. The statement will be ignored. [unsupported-syntax]
 
       v
    5| {
@@ -275,7 +291,7 @@ Cannot use `block` statements in a library file. The statement will be ignored.
 
 Error --------------------------------------------------------------------------------------- libs/invalid-nested.js:9:1
 
-Cannot use `if` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements in a library file. The statement will be ignored. [unsupported-syntax]
 
        v----------
     9| if (true) {
@@ -310,7 +326,7 @@ Cannot use type without exactly 1 type argument. [nonpolymorphic-type-app]
 
 Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:3:3
 
-Cannot use `if` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements in a library file. The statement will be ignored. [unsupported-syntax]
 
    3|   if (true) {} // error
         ^^^^^^^^^^^^
@@ -318,12 +334,28 @@ Cannot use `if` statements in a library file. The statement will be ignored. [un
 
 Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:3:3
 
-Cannot use `if` statements with in `declare module`. The statement will be ignored. [unsupported-syntax]
+Cannot use if statements with in `declare module`. The statement will be ignored. [unsupported-syntax]
 
    3|   if (true) {} // error
         ^^^^^^^^^^^^
 
 
+Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:4:3
+
+Cannot use value export statements in a library file. The statement will be ignored. [unsupported-syntax]
+
+   4|   export const foo = ''; // error
+        ^^^^^^^^^^^^^^^^^^^^^^
+
+
+Error ------------------------------------------------------------------------------- libs/unsupported-statements.js:4:3
+
+Cannot use value export statements with in `declare module`. The statement will be ignored. [unsupported-syntax]
+
+   4|   export const foo = ''; // error
+        ^^^^^^^^^^^^^^^^^^^^^^
+
+
 Error -------------------------------------------------------------------------------------------------------- a.js:5:17
 
 Cannot assign `0` to `x` because number [1] is incompatible with string [2]. [incompatible-type]
@@ -422,4 +454,4 @@ Suppression is missing a code. Please update this suppression to use an error co
 
 
 
-Found 20 errors and 1 warning
+Found 22 errors and 1 warning
diff --git a/tests/liberr/libs/unsupported-statements.js b/tests/liberr/libs/unsupported-statements.js
index bfa6ad341cb..07f882e587c 100644
--- a/tests/liberr/libs/unsupported-statements.js
+++ b/tests/liberr/libs/unsupported-statements.js
@@ -1,4 +1,6 @@
 declare module 'contains-unsupported-statements' {
   declare const a: number;
   if (true) {} // error
+  export const foo = ''; // error
+  export type Bar = string; // ok
 }
diff --git a/tests/poorly_formed_exports/poorly_formed_exports.exp b/tests/poorly_formed_exports/poorly_formed_exports.exp
index ff0ccf27e3d..44dea08e6cd 100644
--- a/tests/poorly_formed_exports/poorly_formed_exports.exp
+++ b/tests/poorly_formed_exports/poorly_formed_exports.exp
@@ -1,7 +1,7 @@
 FLOW STATUS:
 Error ------------------------------------------------------------------------------------------------- libs/libs.js:3:1
 
-Cannot use `block` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use block statements in a library file. The statement will be ignored. [unsupported-syntax]
 
       v
    3| {
diff --git a/tests/poorly_formed_exports_config_false/poorly_formed_exports_config_false.exp b/tests/poorly_formed_exports_config_false/poorly_formed_exports_config_false.exp
index dd96be0c37c..74d165ae54e 100644
--- a/tests/poorly_formed_exports_config_false/poorly_formed_exports_config_false.exp
+++ b/tests/poorly_formed_exports_config_false/poorly_formed_exports_config_false.exp
@@ -1,7 +1,7 @@
 FLOW STATUS:
 Error ------------------------------------------------------------------------------------------------- libs/libs.js:3:1
 
-Cannot use `block` statements in a library file. The statement will be ignored. [unsupported-syntax]
+Cannot use block statements in a library file. The statement will be ignored. [unsupported-syntax]
 
       v
    3| {