diff --git a/gui/slidervalue.cpp b/gui/slidervalue.cpp
index c83456b..972d1f7 100644
--- a/gui/slidervalue.cpp
+++ b/gui/slidervalue.cpp
@@ -396,8 +396,10 @@
 	return 0;
 }
 
-int GUISliderValue::NotifyVarChange(std::string varName, std::string value)
+int GUISliderValue::NotifyVarChange(const std::string& varName, const std::string& value)
 {
+	GUIObject::NotifyVarChange(varName, value);
+
 	if (mLabel)
 		mLabel->NotifyVarChange(varName, value);
 	if (varName == mVariable) {