diff --git a/Source/cmDSPWriter.cxx b/Source/cmDSPWriter.cxx
index 5c739cad1..c3ad622e8 100644
--- a/Source/cmDSPWriter.cxx
+++ b/Source/cmDSPWriter.cxx
@@ -325,6 +325,7 @@ void cmDSPWriter::WriteCustomRule(std::ostream& fout,
       }
     fout << "\n";
 
+    fout << "# PROP Ignore_Default_Tool 1\n";
     fout << "# Begin Custom Build\n\n";
     if(outputs.size() == 0)
       {