diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index 31732ddf37c..515a1a84c14 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -4289,6 +4289,8 @@ void tst_Moc::mocJsonOutput()
             return "Error waiting for diff process to finish.";
         return diffProc.readAllStandardOutput();
 #else
+        Q_UNUSED(actual);
+        Q_UNUSED(expected);
         return "Cannot launch diff. Please check allmocs.json and allmocs_baseline.json on disk.";
 #endif
     };