diff -up grep-2.5.3/src/search.c.bz479152 grep-2.5.3/src/search.c
--- grep-2.5.3/src/search.c.bz479152	2009-01-08 09:57:12.000000000 +0100
+++ grep-2.5.3/src/search.c	2009-01-08 09:58:57.000000000 +0100
@@ -757,7 +757,7 @@ EXECUTE_FCT(Fexecute)
   const char *last_char = NULL;
 #endif /* MBS_SUPPORT */
 
-  for (beg = start_ptr ? start_ptr : buf; beg <= buf + size; beg++)
+  for (beg = start_ptr ? start_ptr : buf; beg < buf + size; beg++)
     {
       size_t offset = kwsexec (kwset, beg, buf + size - beg, &kwsmatch);
       if (offset == (size_t) -1)