diff --git a/Source/kwsys/RegularExpression.hxx.in b/Source/kwsys/RegularExpression.hxx.in
index 3cc338c10d..5b6b451c38 100644
--- a/Source/kwsys/RegularExpression.hxx.in
+++ b/Source/kwsys/RegularExpression.hxx.in
@@ -276,7 +276,7 @@ private:
   char  regstart;                       // Internal use only
   char  reganch;                        // Internal use only
   const char* regmust;                  // Internal use only
-  int   regmlen;                        // Internal use only
+  unsigned long regmlen;                // Internal use only
   char* program;   
   int   progsize;
   const char* searchstring;