diff --git a/test/built-ins/Temporal/Calendar/prototype/dateAdd/overflow-invalid-string.js b/test/built-ins/Temporal/Calendar/prototype/dateAdd/overflow-invalid-string.js
index 3197c54007c..df173c933f7 100644
--- a/test/built-ins/Temporal/Calendar/prototype/dateAdd/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/Calendar/prototype/dateAdd/overflow-invalid-string.js
@@ -17,6 +17,11 @@ features: [Temporal, arrow-function]
 const calendar = new Temporal.Calendar("iso8601");
 const date = new Temporal.PlainDate(2000, 5, 2, calendar);
 const duration = new Temporal.Duration(3, 3, 0, 3);
-assert.throws(RangeError,
-    () => calendar.dateAdd(date, duration, { overflow: "other string" }),
-    "Value for overflow not one of the allowed string values");
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => calendar.dateAdd(date, duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/Calendar/prototype/dateFromFields/overflow-invalid-string.js b/test/built-ins/Temporal/Calendar/prototype/dateFromFields/overflow-invalid-string.js
index 6cc0d01724d..28e81de7ceb 100644
--- a/test/built-ins/Temporal/Calendar/prototype/dateFromFields/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/Calendar/prototype/dateFromFields/overflow-invalid-string.js
@@ -17,6 +17,12 @@ features: [Temporal, arrow-function]
 ---*/
 
 const calendar = new Temporal.Calendar("iso8601");
-assert.throws(RangeError, () => calendar.dateFromFields({ year: 2000, month: 5, day: 2 },
-      { overflow: "other string" }),
-    "Value for overflow not one of the allowed string values");
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => calendar.dateFromFields({ year: 2000, month: 5, day: 2 },
+      { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/Calendar/prototype/monthDayFromFields/overflow-invalid-string.js b/test/built-ins/Temporal/Calendar/prototype/monthDayFromFields/overflow-invalid-string.js
index 2e87dc1a67a..6844c7e3d2b 100644
--- a/test/built-ins/Temporal/Calendar/prototype/monthDayFromFields/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/Calendar/prototype/monthDayFromFields/overflow-invalid-string.js
@@ -17,4 +17,11 @@ features: [Temporal]
 ---*/
 
 const calendar = new Temporal.Calendar("iso8601");
-assert.throws(RangeError, () => calendar.monthDayFromFields({ year: 2000, month: 5, day: 2 }, { overflow: "other string" }));
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => calendar.monthDayFromFields({ year: 2000, month: 5, day: 2 }, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/Calendar/prototype/yearMonthFromFields/overflow-invalid-string.js b/test/built-ins/Temporal/Calendar/prototype/yearMonthFromFields/overflow-invalid-string.js
index 99ffe6af277..77c14141097 100644
--- a/test/built-ins/Temporal/Calendar/prototype/yearMonthFromFields/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/Calendar/prototype/yearMonthFromFields/overflow-invalid-string.js
@@ -17,4 +17,11 @@ features: [Temporal]
 ---*/
 
 const calendar = new Temporal.Calendar("iso8601");
-assert.throws(RangeError, () => calendar.yearMonthFromFields({ year: 2000, month: 5 }, { overflow: "other string" }));
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => calendar.yearMonthFromFields({ year: 2000, month: 5 }, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/PlainDate/from/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDate/from/overflow-invalid-string.js
index f04f77f745b..27e499961c5 100644
--- a/test/built-ins/Temporal/PlainDate/from/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDate/from/overflow-invalid-string.js
@@ -34,8 +34,14 @@ const invalidOverflow = [
   "CONSTRAIN",
   "constra\u0131n",
 ];
-validItems.forEach((item) => {
-  invalidOverflow.forEach((overflow) => {
-    assert.throws(RangeError, () => Temporal.PlainDate.from(item, { overflow }));
-  });
-});
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const item of validItems) {
+  for (const overflow of badOverflows) {
+    assert.throws(
+      RangeError,
+      () => Temporal.PlainDate.from(item, { overflow }),
+      `invalid overflow ("${overflow}")`
+    );
+  }
+}
diff --git a/test/built-ins/Temporal/PlainDate/prototype/add/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDate/prototype/add/overflow-invalid-string.js
index 66282d2a6c3..6c7b65fd879 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/add/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/add/overflow-invalid-string.js
@@ -18,6 +18,12 @@ features: [Temporal]
 
 const date = new Temporal.PlainDate(2000, 5, 2);
 const duration = new Temporal.Duration(3, 3, 0, 3);
-for (const overflow of ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"]) {
-  assert.throws(RangeError, () => date.add(duration, { overflow }));
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => date.add(duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
 }
diff --git a/test/built-ins/Temporal/PlainDate/prototype/subtract/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDate/prototype/subtract/overflow-invalid-string.js
index d3cbd6e8074..9387c6aff46 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/subtract/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/subtract/overflow-invalid-string.js
@@ -18,6 +18,12 @@ features: [Temporal]
 
 const date = new Temporal.PlainDate(2000, 5, 2);
 const duration = new Temporal.Duration(3, 3, 0, 3);
-for (const overflow of ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"]) {
-  assert.throws(RangeError, () => date.subtract(duration, { overflow }));
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => date.subtract(duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
 }
diff --git a/test/built-ins/Temporal/PlainDate/prototype/with/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDate/prototype/with/overflow-invalid-string.js
index d35f66be86b..acef874825b 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/with/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/with/overflow-invalid-string.js
@@ -17,6 +17,12 @@ features: [Temporal]
 ---*/
 
 const date = new Temporal.PlainDate(2000, 5, 2);
-["", "CONSTRAIN", "balance", "other string"].forEach((overflow) =>
-  assert.throws(RangeError, () => date.with({ month: 8 }, { overflow }))
-);
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => date.with({ month: 8 }, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/PlainDateTime/from/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDateTime/from/overflow-invalid-string.js
index 41673499f72..1786ed59049 100644
--- a/test/built-ins/Temporal/PlainDateTime/from/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDateTime/from/overflow-invalid-string.js
@@ -31,6 +31,14 @@ const validValues = [
   { year: 2000, month: 5, day: 2, hour: 12 },
   "2000-05-02T12:00",
 ];
-validValues.forEach((value) => {
-  assert.throws(RangeError, () => Temporal.PlainDateTime.from(value, { overflow: "other string" }));
-});
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const value of validValues) {
+  for (const overflow of badOverflows) {
+    assert.throws(
+      RangeError,
+      () => Temporal.PlainDateTime.from(value, { overflow }),
+      `invalid overflow ("${overflow}")`
+    );
+  }
+}
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/add/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDateTime/prototype/add/overflow-invalid-string.js
index 40124a8f32d..6ce6ecc29de 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/add/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/add/overflow-invalid-string.js
@@ -21,11 +21,12 @@ features: [Temporal]
 const datetime = new Temporal.PlainDateTime(2000, 5, 2, 12);
 const duration = new Temporal.Duration(3, 3, 0, 3, 3);
 
-const badOverflows = ['', 'CONSTRAIN', 'balance', "other string"];
-badOverflows.forEach((overflow) => {
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
   assert.throws(
     RangeError,
     () => datetime.add({ months: 1 }, { overflow }),
     `invalid overflow ("${overflow}")`
   );
-});
+}
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/subtract/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDateTime/prototype/subtract/overflow-invalid-string.js
index 1e1f1761c81..c3e4b694f44 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/subtract/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/subtract/overflow-invalid-string.js
@@ -20,4 +20,11 @@ features: [Temporal]
 
 const date = new Temporal.PlainDateTime(2000, 5, 2, 12);
 const duration = new Temporal.Duration(3, 3, 0, 3, 3);
-assert.throws(RangeError, () => date.subtract(duration, { overflow: "other string" }));
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => date.subtract(duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/with/overflow-invalid-string.js b/test/built-ins/Temporal/PlainDateTime/prototype/with/overflow-invalid-string.js
index c23b9e9e970..4d3b05b0eac 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/with/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/with/overflow-invalid-string.js
@@ -18,10 +18,12 @@ features: [Temporal]
 ---*/
 
 const datetime = new Temporal.PlainDateTime(2000, 5, 2, 12);
-const badOverflows = ["", "CONSTRAIN", "balance", "other string"];
-badOverflows.forEach((overflow) => {
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
   assert.throws(
     RangeError,
     () => datetime.with({ minute: 45 }, { overflow }),
-    `invalid overflow string (${overflow})`);
-});
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/PlainMonthDay/from/overflow-invalid-string.js b/test/built-ins/Temporal/PlainMonthDay/from/overflow-invalid-string.js
index c2427006fdc..48ccf843643 100644
--- a/test/built-ins/Temporal/PlainMonthDay/from/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainMonthDay/from/overflow-invalid-string.js
@@ -27,6 +27,14 @@ const validValues = [
   { monthCode: "M05", day: 2 },
   "05-02",
 ];
-validValues.forEach((value) => {
-  assert.throws(RangeError, () => Temporal.PlainMonthDay.from(value, { overflow: "other string" }));
-});
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const value of validValues) {
+  for (const overflow of badOverflows) {
+    assert.throws(
+      RangeError,
+      () => Temporal.PlainMonthDay.from(value, { overflow }),
+      `invalid overflow ("${overflow}")`
+    );
+  }
+}
diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/with/overflow-invalid-string.js b/test/built-ins/Temporal/PlainMonthDay/prototype/with/overflow-invalid-string.js
index 5ed47e97538..0036dfe6380 100644
--- a/test/built-ins/Temporal/PlainMonthDay/prototype/with/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/with/overflow-invalid-string.js
@@ -17,6 +17,12 @@ features: [Temporal]
 ---*/
 
 const monthday = new Temporal.PlainMonthDay(5, 2);
-for (const overflow of ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"]) {
-  assert.throws(RangeError, () => monthday.with({ day: 8 }, { overflow }));
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => monthday.with({ day: 8 }, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
 }
diff --git a/test/built-ins/Temporal/PlainTime/from/overflow-invalid-string.js b/test/built-ins/Temporal/PlainTime/from/overflow-invalid-string.js
index 856d071453e..dcefde8a682 100644
--- a/test/built-ins/Temporal/PlainTime/from/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainTime/from/overflow-invalid-string.js
@@ -19,8 +19,14 @@ const validValues = [
   { hour: 12 },
   "12:00",
 ];
-validValues.forEach((value) => {
-  ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"].forEach((overflow) => {
-    assert.throws(RangeError, () => Temporal.PlainTime.from(value, { overflow }));
-  });
-});
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const value of validValues) {
+  for (const overflow of badOverflows) {
+    assert.throws(
+      RangeError,
+      () => Temporal.PlainTime.from(value, { overflow }),
+      `invalid overflow ("${overflow}")`
+    );
+  }
+}
diff --git a/test/built-ins/Temporal/PlainTime/prototype/with/overflow-invalid-string.js b/test/built-ins/Temporal/PlainTime/prototype/with/overflow-invalid-string.js
index 796cec5fcf3..dc50e7795bc 100644
--- a/test/built-ins/Temporal/PlainTime/prototype/with/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainTime/prototype/with/overflow-invalid-string.js
@@ -16,6 +16,12 @@ features: [Temporal]
 
 const time = new Temporal.PlainTime(12);
 const values = ["", "CONSTRAIN", "balance", "other string"];
-for (const overflow of values) {
-  assert.throws(RangeError, () => time.with({ minute: 45 }, { overflow }));
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => time.with({ minute: 45 }, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
 }
diff --git a/test/built-ins/Temporal/PlainYearMonth/from/overflow-invalid-string.js b/test/built-ins/Temporal/PlainYearMonth/from/overflow-invalid-string.js
index d30774eece5..11335f2481a 100644
--- a/test/built-ins/Temporal/PlainYearMonth/from/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainYearMonth/from/overflow-invalid-string.js
@@ -27,8 +27,14 @@ const validValues = [
   { year: 2000, month: 5 },
   "2000-05",
 ];
-validValues.forEach((value) => {
-  ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"].forEach((overflow) => {
-    assert.throws(RangeError, () => Temporal.PlainYearMonth.from(value, { overflow }));
-  });
-});
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const value of validValues) {
+  for (const overflow of badOverflows) {
+    assert.throws(
+      RangeError,
+      () => Temporal.PlainYearMonth.from(value, { overflow }),
+      `invalid overflow ("${overflow}")`
+    );
+  }
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/add/overflow-invalid-string.js b/test/built-ins/Temporal/PlainYearMonth/prototype/add/overflow-invalid-string.js
index 4913de46a29..1633f1b6544 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/add/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/add/overflow-invalid-string.js
@@ -20,6 +20,12 @@ features: [Temporal]
 
 const yearmonth = new Temporal.PlainYearMonth(2000, 5);
 const duration = new Temporal.Duration(1, 1);
-for (const overflow of ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"]) {
-  assert.throws(RangeError, () => yearmonth.add(duration, { overflow }));
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => yearmonth.add(duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
 }
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/subtract/overflow-invalid-string.js b/test/built-ins/Temporal/PlainYearMonth/prototype/subtract/overflow-invalid-string.js
index 8c2efb855a7..46286d5a6a2 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/subtract/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/subtract/overflow-invalid-string.js
@@ -20,6 +20,12 @@ features: [Temporal]
 
 const yearmonth = new Temporal.PlainYearMonth(2000, 5);
 const duration = new Temporal.Duration(1, 1);
-for (const overflow of ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"]) {
-  assert.throws(RangeError, () => yearmonth.subtract(duration, { overflow }));
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => yearmonth.subtract(duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
 }
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/with/overflow-invalid-string.js b/test/built-ins/Temporal/PlainYearMonth/prototype/with/overflow-invalid-string.js
index 587c66754c8..4684d597f3e 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/with/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/with/overflow-invalid-string.js
@@ -17,6 +17,12 @@ features: [Temporal]
 ---*/
 
 const yearmonth = new Temporal.PlainYearMonth(2000, 5);
-for (const overflow of ["", "CONSTRAIN", "balance", "other string", "constra\u0131n"]) {
-  assert.throws(RangeError, () => yearmonth.with({ month: 8 }, { overflow }));
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => yearmonth.with({ month: 8 }, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
 }
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/overflow-invalid-string.js b/test/built-ins/Temporal/ZonedDateTime/from/overflow-invalid-string.js
index 5913d3e7f96..e8406c57e37 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/overflow-invalid-string.js
@@ -32,6 +32,14 @@ const validValues = [
   { year: 2000, month: 5, day: 2, hour: 12, timeZone: "UTC" },
   "2001-09-09T01:46:40.987654321+00:00[UTC]",
 ];
-validValues.forEach((value) => {
-  assert.throws(RangeError, () => Temporal.ZonedDateTime.from(value, { overflow: "other string" }));
-});
+
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const value of validValues) {
+  for (const overflow of badOverflows) {
+    assert.throws(
+      RangeError,
+      () => Temporal.ZonedDateTime.from(value, { overflow }),
+      `invalid overflow ("${overflow}")`
+    );
+  }
+}
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/add/overflow-invalid-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/add/overflow-invalid-string.js
index 4c88b568784..ede72ad4a96 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/add/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/add/overflow-invalid-string.js
@@ -20,4 +20,11 @@ features: [Temporal]
 
 const datetime = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
 const duration = new Temporal.Duration(0, 0, 0, 1);
-assert.throws(RangeError, () => datetime.add(duration, { overflow: "other string" }));
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => datetime.add(duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/subtract/overflow-invalid-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/subtract/overflow-invalid-string.js
index 8c144ef70d0..7a7d4fd1206 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/subtract/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/subtract/overflow-invalid-string.js
@@ -20,4 +20,11 @@ features: [Temporal]
 
 const datetime = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
 const duration = new Temporal.Duration(0, 0, 0, 1);
-assert.throws(RangeError, () => datetime.subtract(duration, { overflow: "other string" }));
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => datetime.subtract(duration, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/with/overflow-invalid-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/with/overflow-invalid-string.js
index 96d5ab3799d..843437f59fd 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/with/overflow-invalid-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/with/overflow-invalid-string.js
@@ -18,4 +18,11 @@ features: [Temporal]
 ---*/
 
 const datetime = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
-assert.throws(RangeError, () => datetime.with({ minute: 45 }, { overflow: "other string" }));
+const badOverflows = ["", "CONSTRAIN", "balance", "other string", "constra\u0131n", "reject\0"];
+for (const overflow of badOverflows) {
+  assert.throws(
+    RangeError,
+    () => datetime.with({ minute: 45 }, { overflow }),
+    `invalid overflow ("${overflow}")`
+  );
+}