diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index fabfd3596..870fd6f48 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -3162,6 +3162,10 @@ const char *cmMakefile::GetProperty(const char* prop)
 const char *cmMakefile::GetProperty(const char* prop,
                                     cmProperty::ScopeType scope)
 {
+  if(!prop)
+    {
+    return 0;
+    }
   // watch for specific properties
   static std::string output;
   output = "";
diff --git a/Source/cmake.cxx b/Source/cmake.cxx
index 1f7a7464b..10db0adc3 100644
--- a/Source/cmake.cxx
+++ b/Source/cmake.cxx
@@ -3606,6 +3606,10 @@ const char *cmake::GetProperty(const char* prop)
 
 const char *cmake::GetProperty(const char* prop, cmProperty::ScopeType scope)
 {
+  if(!prop)
+    {
+    return 0;
+    }
   bool chain = false;
 
   // watch for special properties