diff --git a/src_main/core/piobject.h b/src_main/core/piobject.h
index afa76327..2e1e9207 100755
--- a/src_main/core/piobject.h
+++ b/src_main/core/piobject.h
@@ -633,11 +633,12 @@ public:
 				if (i.performer) {
 					i.performer->postQueuedEvent(__QueuedEvent(i.slot, i.dest, i.dest_o, sender));
 				} else {
-					if (sender->thread_safe_) i.dest_o->mutex_.lock();
+					bool th = sender->thread_safe_;
+					if (th) i.dest_o->mutex_.lock();
 					i.dest_o->emitter_ = sender;
 					((void( *)(void * ))i.slot)(i.dest);
 					i.dest_o->emitter_ = 0;
-					if (sender->thread_safe_) i.dest_o->mutex_.unlock();
+					if (th) i.dest_o->mutex_.unlock();
 				}
 #ifdef PIP_CXX11_SUPPORT
 			}