diff --git a/autotests/mock_effectshandler.h b/autotests/mock_effectshandler.h
index 1c844b6e3a..beed94a1d8 100644
--- a/autotests/mock_effectshandler.h
+++ b/autotests/mock_effectshandler.h
@@ -131,7 +131,7 @@ public:
         return nullptr;
     }
     bool grabKeyboard(KWin::Effect *) override {
-        return nullptr;
+        return false;
     }
     bool hasDecorationShadows() const override {
         return false;