diff --git a/Source/cmVariableWatch.cxx b/Source/cmVariableWatch.cxx
index 21b910dea..21acd3b7e 100644
--- a/Source/cmVariableWatch.cxx
+++ b/Source/cmVariableWatch.cxx
@@ -53,11 +53,13 @@ cmVariableWatch::~cmVariableWatch()
 }
 
 void cmVariableWatch::AddWatch(const std::string& variable,
-                               WatchMethod method, void* client_data /*=0*/)
+                               WatchMethod method, void* client_data /*=0*/,
+                               DeleteData delete_data /*=0*/)
 {
   cmVariableWatch::Pair* p = new cmVariableWatch::Pair;
   p->Method = method;
   p->ClientData = client_data;
+  p->DeleteDataCall = delete_data;
   cmVariableWatch::VectorOfPairs* vp = &this->WatchMap[variable];
   cmVariableWatch::VectorOfPairs::size_type cc;
   for ( cc = 0; cc < vp->size(); cc ++ )
diff --git a/Source/cmVariableWatch.h b/Source/cmVariableWatch.h
index 45273e5ae..d66681598 100644
--- a/Source/cmVariableWatch.h
+++ b/Source/cmVariableWatch.h
@@ -26,6 +26,7 @@ class cmVariableWatch
 public:
   typedef void (*WatchMethod)(const std::string& variable, int access_type,
     void* client_data, const char* newValue, const cmMakefile* mf);
+  typedef void (*DeleteData)(void* client_data);
 
   cmVariableWatch();
   ~cmVariableWatch();
@@ -34,7 +35,7 @@ public:
    * Add watch to the variable
    */
   void AddWatch(const std::string& variable, WatchMethod method,
-                void* client_data=0);
+                void* client_data=0, DeleteData delete_data=0);
   void RemoveWatch(const std::string& variable, WatchMethod method);
 
   /**
@@ -67,7 +68,15 @@ protected:
   {
     WatchMethod Method;
     void*        ClientData;
-    Pair() : Method(0), ClientData(0) {}
+    DeleteData   DeleteDataCall;
+    Pair() : Method(0), ClientData(0), DeleteDataCall(0) {}
+    ~Pair()
+      {
+      if (this->DeleteDataCall && this->ClientData)
+        {
+        this->DeleteDataCall(this->ClientData);
+        }
+      }
   };
 
   typedef std::vector< Pair* > VectorOfPairs;