diff --git a/test/built-ins/Temporal/Now/plainDateTimeISO/timezone-string-datetime.js b/test/built-ins/Temporal/Now/plainDateTimeISO/timezone-string-datetime.js
index dc6b5da2b4..bba11d7633 100644
--- a/test/built-ins/Temporal/Now/plainDateTimeISO/timezone-string-datetime.js
+++ b/test/built-ins/Temporal/Now/plainDateTimeISO/timezone-string-datetime.js
@@ -19,6 +19,14 @@ assert.throws(RangeError, () => Temporal.Now.plainDateTimeISO({ timeZone }), "ba
   "2021-08-19T1730-07:00",
   "2021-08-19T17:30-0700",
   "2021-08-19T1730-0700",
+  "2021-08-19T17:30[UTC]",
+  "2021-08-19T1730[UTC]",
+  "2021-08-19T17:30Z[UTC]",
+  "2021-08-19T1730Z[UTC]",
+  "2021-08-19T17:30-07:00[UTC]",
+  "2021-08-19T1730-07:00[UTC]",
+  "2021-08-19T17:30-0700[UTC]",
+  "2021-08-19T1730-0700[UTC]",
 ].forEach((timeZone) => {
   Temporal.Now.plainDateTimeISO(timeZone);
   Temporal.Now.plainDateTimeISO({ timeZone });