diff --git a/RegularExpression.hxx.in b/RegularExpression.hxx.in
index 3e12855cf713a63911a4cd18fe1bd15dce8d6e14..31997779aa9bc15137a58e82eeb17a57148ce082 100644
--- a/RegularExpression.hxx.in
+++ b/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;