diff --git a/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm b/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm
index 98abd505d4d9b..d3f1551533304 100644
--- a/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm
+++ b/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm
@@ -131,10 +131,13 @@ - (void)handleEvent:(NSEvent*)event callback:(FlutterAsyncKeyCallback)callback {
         return;
       }
       break;
-    default: {
-      NSAssert(false, @"Unexpected key event type (got %lu).", event.type);
-      callback(false);
-    }
+    default:
+      [[unlikely]] {
+        NSAssert(false, @"Unexpected key event type (got %lu).", event.type);
+        callback(false);
+        // This should not happen. Return to suppress clang-tidy warning on `type` being nil.
+        return;
+      }
   }
   _previouslyPressedFlags = modifierFlags;
   NSMutableDictionary* keyMessage = [@{