diff --git a/parse.y b/parse.y
index 0e4a735..5b59419 100644
--- a/parse.y
+++ b/parse.y
@@ -6230,10 +6230,12 @@ parser_encode_length(struct parser_params *parser, const char *name, long len)
 	if (rb_memcicmp(name + nlen + 1, "unix", 4) == 0)
 	    return nlen;
     }
-    if (len > 4 && name[nlen = len - 5] == '-') {
+    if (len > 4 && name[nlen = len - 4] == '-') {
 	if (rb_memcicmp(name + nlen + 1, "dos", 3) == 0)
 	    return nlen;
-	if (rb_memcicmp(name + nlen + 1, "mac", 3) == 0)
+	if (rb_memcicmp(name + nlen + 1, "mac", 3) == 0 &&
+	    !(len == 8 && rb_memcicmp(name, "utf8-mac", len) == 0) &&
+	    !(len == 9 && rb_memcicmp(name, "utf-8-mac", len) == 0))
 	    return nlen;
     }
     return len;