diff --git a/lib/rule-tester/flat-rule-tester.js b/lib/rule-tester/flat-rule-tester.js
index ce46e2f7b1a..8b464098f51 100644
--- a/lib/rule-tester/flat-rule-tester.js
+++ b/lib/rule-tester/flat-rule-tester.js
@@ -1083,7 +1083,7 @@ class FlatRuleTester {
             if (item.name) {
                 assert.ok(typeof item.name === "string", "Optional test case property 'name' must be a string");
             }
-            assert.ok(typeof item.error === "object",
+            assert.ok(typeof item.error === "object" && item.error !== null,
                 "Test case property 'error' must be an object");
 
             assert.ok(typeof item.error.name === "string" || typeof item.error.message === "string" || item.error.message instanceof RegExp,