diff --git a/.changeset/eight-crews-clean.md b/.changeset/eight-crews-clean.md
new file mode 100644
index 00000000000..094803988e7
--- /dev/null
+++ b/.changeset/eight-crews-clean.md
@@ -0,0 +1,5 @@
+---
+'graphql-language-service': patch
+---
+
+Fix JSON schema for custom scalars validation
diff --git a/packages/graphql-language-service/src/utils/getVariablesJSONSchema.ts b/packages/graphql-language-service/src/utils/getVariablesJSONSchema.ts
index 63fe1a2324c..0b6833e599f 100644
--- a/packages/graphql-language-service/src/utils/getVariablesJSONSchema.ts
+++ b/packages/graphql-language-service/src/utils/getVariablesJSONSchema.ts
@@ -144,9 +144,8 @@ function getJSONSchemaFromGraphQLType(
     definition.enum = type.getValues().map(val => val.name);
   }
 
-  if (isScalarType(type)) {
-    // I think this makes sense for custom scalars?
-    definition.type = scalarTypesMap[type.name] ?? 'any';
+  if (isScalarType(type) && scalarTypesMap[type.name]) {
+    definition.type = scalarTypesMap[type.name];
   }
   if (isListType(type)) {
     definition.type = 'array';