diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 63bf03bdda..014ef67932 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -1759,6 +1759,10 @@ void cmMakefile::AddDefinition(const char* name, bool value)
 
 void cmMakefile::CheckForUnusedVariables() const
 {
+  if (!this->WarnUnused)
+    {
+    return;
+    }
   const cmDefinitions& defs = this->Internal->VarStack.top();
   const std::set<cmStdString>& locals = defs.LocalKeys();
   std::set<cmStdString>::const_iterator it = locals.begin();