diff --git a/sdk/appconfiguration/app-configuration/test/public/utils/testHelpers.ts b/sdk/appconfiguration/app-configuration/test/public/utils/testHelpers.ts
index 621732b5aa6c..0b143d59669c 100644
--- a/sdk/appconfiguration/app-configuration/test/public/utils/testHelpers.ts
+++ b/sdk/appconfiguration/app-configuration/test/public/utils/testHelpers.ts
@@ -163,11 +163,12 @@ export async function assertThrowsRestError(
     await testFunction();
     assert.fail(`${message}: No error thrown`);
   } catch (err) {
-    if (!(err instanceof RestError)) {
+    if (!(err instanceof Error)) {
       throw new Error("Error is not recognized");
     }
     if (err.name === "RestError") {
-      assert.equal(expectedStatusCode, err.statusCode, message);
+      const restError = err as RestError;
+      assert.equal(expectedStatusCode, restError.statusCode, message);
       return err;
     }