diff --git a/Source/cmCTest.cxx b/Source/cmCTest.cxx
index 780618af0..1b5c8e67d 100644
--- a/Source/cmCTest.cxx
+++ b/Source/cmCTest.cxx
@@ -24,6 +24,7 @@
 # include "curl/curl.h"
 #endif
 
+#include <stdlib.h> // required for atoi
 #include <stdio.h>
 #include <time.h>
 #include <math.h>
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index ab178a029..a71de1b8a 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -29,7 +29,7 @@
 #include "cmVariableWatch.h"
 #include "cmake.h"
 #include <stdio.h>  // required for sprintf
-
+#include <stdlib.h> // required for atoi
 // default is not to be building executables
 cmMakefile::cmMakefile()
 {
diff --git a/Source/cmStringCommand.cxx b/Source/cmStringCommand.cxx
index a4d55181b..e8d6bc14f 100644
--- a/Source/cmStringCommand.cxx
+++ b/Source/cmStringCommand.cxx
@@ -15,7 +15,7 @@
 
 =========================================================================*/
 #include "cmStringCommand.h"
-
+#include <stdlib.h> // required for atoi
 //----------------------------------------------------------------------------
 bool cmStringCommand::InitialPass(std::vector<std::string> const& args)
 {
diff --git a/Source/cmake.cxx b/Source/cmake.cxx
index 22e3f58df..3cf11498b 100644
--- a/Source/cmake.cxx
+++ b/Source/cmake.cxx
@@ -36,6 +36,7 @@
 #endif
 
 #include <stdio.h>
+#include <stdlib.h> // required for atoi
 
 #ifdef __APPLE__
 #include <sys/types.h>