diff --git a/gtk2_ardour/luainstance.cc b/gtk2_ardour/luainstance.cc
index d33bc44c8c..73454d0369 100644
--- a/gtk2_ardour/luainstance.cc
+++ b/gtk2_ardour/luainstance.cc
@@ -1114,15 +1114,15 @@ LuaCallback::connect_2 (enum LuaSignal::LuaSignal ls, T ref, PBD::Signal2<void,
 
 template <typename T> void
 LuaCallback::proxy_0 (enum LuaSignal::LuaSignal ls, T ref) {
-	if (!(*_lua_call)((int)ls, ref)) { drop_callback (); /* EMIT SIGNAL */}
+	if (0 == (*_lua_call)((int)ls, ref)) { drop_callback (); /* EMIT SIGNAL */}
 }
 
 template <typename T, typename C1> void
 LuaCallback::proxy_1 (enum LuaSignal::LuaSignal ls, T ref, C1 a1) {
-	if (!(*_lua_call)((int)ls, ref, a1)) { drop_callback (); /* EMIT SIGNAL */}
+	if (0 == (*_lua_call)((int)ls, ref, a1)) { drop_callback (); /* EMIT SIGNAL */}
 }
 
 template <typename T, typename C1, typename C2> void
 LuaCallback::proxy_2 (enum LuaSignal::LuaSignal ls, T ref, C1 a1, C2 a2) {
-	if (!(*_lua_call)((int)ls, ref, a1, a2)) { drop_callback (); /* EMIT SIGNAL */}
+	if (0 == (*_lua_call)((int)ls, ref, a1, a2)) { drop_callback (); /* EMIT SIGNAL */}
 }