diff --git a/src/mcp/util.test.ts b/src/mcp/util.spec.ts
similarity index 99%
rename from src/mcp/util.test.ts
rename to src/mcp/util.spec.ts
index 06b3cac1a2a..1344c950725 100644
--- a/src/mcp/util.test.ts
+++ b/src/mcp/util.spec.ts
@@ -425,6 +425,7 @@ const testCases: TestCase[] = [
       anyOf: [
         { type: "string" },
         { type: "array", items: { type: "object" } },
+        { $ref: "#/$defs/reusableInvalid" },
         { anyOf: [{ type: "boolean" }, { type: "integer" }] },
       ],
     },