}
 
 void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm,
-                    int tz_offset, const char *tz_name)
+                    int tz_offset, int suppress_tz_name)
 {
        struct strbuf munged_fmt = STRBUF_INIT;
        size_t hint = 128;
                        fmt++;
                        break;
                case 'Z':
-                       if (tz_name) {
-                               strbuf_addstr(&munged_fmt, tz_name);
+                       if (suppress_tz_name) {
                                fmt++;
                                break;
                        }