diff --git a/src/macros.h b/src/macros.h
index afe3572..68ea6bc 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -284,7 +284,7 @@
 # define mb_cptr2len(p)	    (enc_utf8 ? utf_ptr2len(p) : (*mb_ptr2len)(p))
 
 # define MB_COPY_CHAR(f, t) if (has_mbyte) mb_copy_char(&f, &t); else *t++ = *f++
-# define MB_CHARLEN(p)	    (has_mbyte ? mb_charlen(p) : STRLEN(p))
+# define MB_CHARLEN(p)	    (has_mbyte ? mb_charlen(p) : (int)STRLEN(p))
 # define PTR2CHAR(p)	    (has_mbyte ? mb_ptr2char(p) : (int)*(p))
 #else
 # define mb_ptr_adv(p)		++p