diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index bf33e70cc..6303ffee8 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -113,7 +113,6 @@ cmMakefile::cmMakefile(const cmMakefile& mf): Internal(new Internals)
   this->Internal->VarInitStack.push(mf.Internal->VarInitStack.top());
   this->Internal->VarUsageStack.push(mf.Internal->VarUsageStack.top());
 
-  this->Prefix = mf.Prefix;
   this->cmStartDirectory = mf.cmStartDirectory;
   this->StartOutputDirectory = mf.StartOutputDirectory;
   this->cmHomeDirectory = mf.cmHomeDirectory;
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index 864f8b06f..321caea9f 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -961,8 +961,6 @@ protected:
   // Check for a an unused variable
   void CheckForUnused(const char* reason, const std::string& name) const;
 
-  std::string Prefix;
-
   std::string cmStartDirectory;
   std::string StartOutputDirectory;
   std::string cmHomeDirectory;