diff --git a/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/instant-string.js b/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/instant-string.js
index cce9d82bae..21e04094d0 100644
--- a/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/instant-string.js
+++ b/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/instant-string.js
@@ -16,9 +16,13 @@ assert.throws(RangeError, () => instance.getNextTransition(str), "date-time + IA
 
 // The following are all valid strings so should not throw:
 
-[
+const valids = [
   "1970-01-01T00:00Z",
   "1970-01-01T00:00+01:00",
   "1970-01-01T00:00Z[America/Vancouver]",
   "1970-01-01T00:00+01:00[America/Vancouver]",
-].forEach((str) => instance.getNextTransition(str));
+];
+for (const str of valids) {
+  const result = instance.getNextTransition(str);
+  assert.sameValue(result, null);
+}
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/instant-string.js b/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/instant-string.js
index 15dab5701c..42a1e8276f 100644
--- a/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/instant-string.js
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/instant-string.js
@@ -16,9 +16,13 @@ assert.throws(RangeError, () => instance.getPreviousTransition(str), "date-time
 
 // The following are all valid strings so should not throw:
 
-[
+const valids = [
   "1970-01-01T00:00Z",
   "1970-01-01T00:00+01:00",
   "1970-01-01T00:00Z[America/Vancouver]",
   "1970-01-01T00:00+01:00[America/Vancouver]",
-].forEach((str) => instance.getPreviousTransition(str));
+];
+for (const str of valids) {
+  const result = instance.getPreviousTransition(str);
+  assert.sameValue(result, null);
+}