diff --git a/common/tool/tool_manager.cpp b/common/tool/tool_manager.cpp
index db5b114575..3233d1cbe5 100644
--- a/common/tool/tool_manager.cpp
+++ b/common/tool/tool_manager.cpp
@@ -123,6 +123,7 @@ struct TOOL_MANAGER::TOOL_STATE
         transitions = aState.transitions;
         vcSettings = aState.vcSettings;
         // do not copy stateStack
+        return *this;
     }
 
     bool operator==( const TOOL_MANAGER::TOOL_STATE& aRhs ) const