diff --git a/gui/progressbar.cpp b/gui/progressbar.cpp
index 9c80eb4..83de4d1 100644
--- a/gui/progressbar.cpp
+++ b/gui/progressbar.cpp
@@ -172,8 +172,10 @@
 	return 2;
 }
 
-int GUIProgressBar::NotifyVarChange(std::string varName, std::string value)
+int GUIProgressBar::NotifyVarChange(const std::string& varName, const std::string& value)
 {
+	GUIObject::NotifyVarChange(varName, value);
+
 	if(!isConditionTrue())
 		return 0;