diff --git a/src/charset.c b/src/charset.c
index cc02563..5b0e71c 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -187,9 +187,14 @@
 		if (VIM_ISDIGIT(*p))
 		    c2 = getdigits(&p);
 		else
+#ifdef FEAT_MBYTE
+		     if (has_mbyte)
+		    c2 = mb_ptr2char_adv(&p);
+		else
+#endif
 		    c2 = *p++;
 	    }
-	    if (c <= 0 || (c2 < c && c2 != -1) || c2 >= 256
+	    if (c <= 0 || c >= 256 || (c2 < c && c2 != -1) || c2 >= 256
 						 || !(*p == NUL || *p == ','))
 		return FAIL;