diff --git a/time.c b/time.c
index cda91a38a6..51939111b3 100644
--- a/time.c
+++ b/time.c
@@ -4194,7 +4194,7 @@ time_isdst(VALUE time)
 static VALUE
 time_zone_name(const char *zone)
 {
-    VALUE name = rb_usascii_str_new_cstr(zone);
+    VALUE name = rb_usascii_str_new_cstr(zone); /* zone may be ASCII-8BIT on Windows */
     if (!rb_enc_str_asciionly_p(name)) {
 	name = rb_external_str_with_enc(name, rb_locale_encoding());
     }