--- a/src/server/server_decoration_interface.cpp

+++ b/src/server/server_decoration_interface.cpp

@@ -117,6 +117,8 @@ static uint32_t modeWayland(ServerSideDe

     default:

         Q_UNREACHABLE();

     }

+    // missing return statement

+    return ORG_KDE_KWIN_SERVER_DECORATION_MODE_NONE;

 }

 }