diff --git a/edb/server/compiler/explain/to_json.py b/edb/server/compiler/explain/to_json.py
index fe4a8da5b3b..16bd7ad7ddb 100644
--- a/edb/server/compiler/explain/to_json.py
+++ b/edb/server/compiler/explain/to_json.py
@@ -21,6 +21,8 @@
 import enum
 import uuid
 
+from edb.ir import statypes
+
 
 class ToJson:
     def to_json(self) -> Any:
@@ -36,4 +38,6 @@ def json_hook(value: Any) -> Any:
         return value.value
     elif isinstance(value, (frozenset, set)):
         return list(value)
+    elif isinstance(value, statypes.ScalarType):
+        return value.to_json()
     raise TypeError(f"Cannot serialize {value!r}")