diff --git a/vitest.config.ts b/vitest.config.ts
index 293d87985..10581cf43 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -15,7 +15,7 @@ const slowTestReporter: Reporter = {
     onTestRunEnd(testModules, unhandledErrors, reason) {
         const tests = testModules
             .flatMap((m) => Array.from(m.children.allTests()))
-            .filter((test) => test.diagnostic().slow);
+            .filter((test) => test.diagnostic()?.slow);
         tests.sort((x, y) => x.diagnostic()?.duration! - y.diagnostic()?.duration!);
         tests.reverse();