diff --git a/.changeset/mean-colts-hunt.md b/.changeset/mean-colts-hunt.md
new file mode 100644
index 000000000..245505dcb
--- /dev/null
+++ b/.changeset/mean-colts-hunt.md
@@ -0,0 +1,5 @@
+---
+"openapi-metadata": patch
+---
+
+[#2123](https://github.com/openapi-ts/openapi-typescript/issues/2123) Fix thunk type detection
diff --git a/packages/openapi-metadata/src/utils/metadata.ts b/packages/openapi-metadata/src/utils/metadata.ts
index 13f19a224..110c1737a 100644
--- a/packages/openapi-metadata/src/utils/metadata.ts
+++ b/packages/openapi-metadata/src/utils/metadata.ts
@@ -35,7 +35,7 @@ export function findType({ metadataKey, prototype, propertyKey }: FindTypeOption
   return reflectedType;
 }
 
-const IS_THUNK_REG = /.+=>[\w\d\s\t\n\r]*/;
+const IS_THUNK_REG = /^.+=>[\w\d\s\t\n\r]*/;
 
 /**
  * Asserts that a value is a thunk value.
diff --git a/packages/openapi-metadata/test/utils/metadata.test.ts b/packages/openapi-metadata/test/utils/metadata.test.ts
index 9bd238511..68059edb5 100644
--- a/packages/openapi-metadata/test/utils/metadata.test.ts
+++ b/packages/openapi-metadata/test/utils/metadata.test.ts
@@ -12,6 +12,14 @@ test("isThunk", () => {
   expect(isThunk(User)).toBe(false);
   expect(isThunk(() => User)).toBe(true);
 
+  class InsideThunk {
+    test() {
+      return [].map(() => {});
+    }
+  }
+  expect(isThunk(InsideThunk)).toBe(false);
+  expect(isThunk(() => InsideThunk)).toBe(true);
+
   expect(
     isThunk(() => {
       return "TESTEST";