diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx
index e2adabe5f..7230a64f9 100644
--- a/Source/cmSystemTools.cxx
+++ b/Source/cmSystemTools.cxx
@@ -2955,3 +2955,12 @@ bool cmSystemTools::StringToLong(const char* str, long* value)
   *value = strtol(str, &endp, 10);
   return (*endp == '\0') && (endp != str) && (errno == 0);
 }
+
+//----------------------------------------------------------------------------
+bool cmSystemTools::StringToULong(const char* str, unsigned long* value)
+{
+  errno = 0;
+  char *endp;
+  *value = strtoul(str, &endp, 10);
+  return (*endp == '\0') && (endp != str) && (errno == 0);
+}
diff --git a/Source/cmSystemTools.h b/Source/cmSystemTools.h
index 6feb6c5bf..8ebb4e325 100644
--- a/Source/cmSystemTools.h
+++ b/Source/cmSystemTools.h
@@ -469,6 +469,7 @@ public:
 
   /** Convert string to long. Expected that the whole string is an integer */
   static bool StringToLong(const char* str, long* value);
+  static bool StringToULong(const char* str, unsigned long* value);
 
 #ifdef _WIN32
   struct WindowsFileRetry