diff --git a/engine/lib/ast.ml b/engine/lib/ast.ml
index cbfc0c4a8..b47006012 100644
--- a/engine/lib/ast.ml
+++ b/engine/lib/ast.ml
@@ -1,5 +1,6 @@
 open Base
 open Utils
+open Ppx_yojson_conv_lib.Yojson_conv.Primitives
 
 module Non_empty_list = struct
   include Non_empty_list
diff --git a/engine/lib/ast_utils.ml b/engine/lib/ast_utils.ml
index 4b22edfa3..4abbed92d 100644
--- a/engine/lib/ast_utils.ml
+++ b/engine/lib/ast_utils.ml
@@ -1,4 +1,5 @@
 open Base
+open Ppx_yojson_conv_lib.Yojson_conv.Primitives
 open Utils
 open Ast
 
diff --git a/engine/lib/diagnostics.ml b/engine/lib/diagnostics.ml
index 6a9303fc0..98676907f 100644
--- a/engine/lib/diagnostics.ml
+++ b/engine/lib/diagnostics.ml
@@ -1,4 +1,5 @@
 open Utils
+open Ppx_yojson_conv_lib.Yojson_conv.Primitives
 module T = Types
 
 module Backend = struct
diff --git a/engine/lib/feature_gate.ml b/engine/lib/feature_gate.ml
index d83299d5c..4b803bfe0 100644
--- a/engine/lib/feature_gate.ml
+++ b/engine/lib/feature_gate.ml
@@ -1,4 +1,5 @@
 open Base
+open Ppx_yojson_conv_lib.Yojson_conv.Primitives
 open Utils
 
 module DefaultSubtype = struct
diff --git a/engine/lib/phase_utils.ml b/engine/lib/phase_utils.ml
index af8c965c0..591460786 100644
--- a/engine/lib/phase_utils.ml
+++ b/engine/lib/phase_utils.ml
@@ -1,4 +1,5 @@
 open Base
+open Ppx_yojson_conv_lib.Yojson_conv.Primitives
 
 module Metadata : sig
   type t = private {
diff --git a/engine/lib/print_rust.ml b/engine/lib/print_rust.ml
index cf891f1f6..295a06a36 100644
--- a/engine/lib/print_rust.ml
+++ b/engine/lib/print_rust.ml
@@ -1,4 +1,5 @@
 open Base
+open Ppx_yojson_conv_lib.Yojson_conv.Primitives
 open Ast
 open Ast.Full
 open Utils
diff --git a/engine/utils/hacspeclib-macro-parser/hacspeclib_macro_parser.ml b/engine/utils/hacspeclib-macro-parser/hacspeclib_macro_parser.ml
index 2b084a0d3..762a5418f 100644
--- a/engine/utils/hacspeclib-macro-parser/hacspeclib_macro_parser.ml
+++ b/engine/utils/hacspeclib-macro-parser/hacspeclib_macro_parser.ml
@@ -1,5 +1,6 @@
 open! Base
 open Angstrom
+open Ppx_yojson_conv_lib.Yojson_conv.Primitives
 
 module BasicParsers = struct
   let is_space = function ' ' | '\t' | '\n' -> true | _ -> false