diff --git a/Source/cmGeneratorExpression.cxx b/Source/cmGeneratorExpression.cxx
index b6fe4146a..861122cc0 100644
--- a/Source/cmGeneratorExpression.cxx
+++ b/Source/cmGeneratorExpression.cxx
@@ -15,8 +15,6 @@
 #include "cmTarget.h"
 #include "assert.h"
 
-#include <cmsys/String.h>
-
 #include "cmGeneratorExpressionEvaluator.h"
 #include "cmGeneratorExpressionLexer.h"
 #include "cmGeneratorExpressionParser.h"