diff --git a/rtgui/progressconnector.h b/rtgui/progressconnector.h
index bec94f0cd..377749b14 100644
--- a/rtgui/progressconnector.h
+++ b/rtgui/progressconnector.h
@@ -114,7 +114,10 @@ class ProgressConnector  {
         	}
 
                 if (qMutex)
+                {
                     delete qMutex;
+                    qMutex = NULL;
+                }
         }
 
         T returnValue(){