diff --git a/compat/utf8proc.c b/compat/utf8proc.c
index dd4ab27f..147da696 100644
--- a/compat/utf8proc.c
+++ b/compat/utf8proc.c
@@ -48,7 +48,7 @@ utf8proc_mbtowc(wchar_t *pwc, const char *s, size_t n)
 	 * *pwc == -1 indicates invalid codepoint
 	 * slen < 0 indicates an error
 	 */
-	slen = utf8proc_iterate(s, n, pwc);
+	slen = utf8proc_iterate(s, n, (utf8proc_int32_t*)pwc);
 	if (*pwc == (wchar_t)-1 || slen < 0)
 		return (-1);
 	return (slen);