diff --git a/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js b/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js
index 727134d7f93..19b586f8060 100644
--- a/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js
+++ b/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js
@@ -9,10 +9,10 @@ info: |
     Intl.Locale( tag [, options] )
 
     ...
-    x. Let fw be ? GetOption(options, "firstDayOfWeek", "string", undefined, undefined).
-    x. If fw is not undefined, then
-       x. Set fw to !WeekdayToString(fw).
-       x. If fw does not match the type sequence (from UTS 35 Unicode Locale Identifier, section 3.2), throw a RangeError exception.
+    22. Let fw be ? GetOption(options, "firstDayOfWeek", string, empty, undefined).
+    23. If fw is not undefined, then
+       a. Set fw to WeekdayToUValue(fw).
+       b. If fw cannot be matched by the type Unicode locale nonterminal, throw a RangeError exception.
     ...
 
 features: [Intl.Locale,Intl.Locale-info]
@@ -23,9 +23,30 @@ const invalidFirstDayOfWeekOptions = [
   "m",
   "mo",
   "longerThan8Chars",
+  "abc\0abc",
+  "abc?",
+  "äöü",
+  "\u6161bc",
+  8,
+  9,
+  10,
+  -1,
+  -10,
+  -100,
+  -1000,
+  8n,
+  9n,
+  10n,
+  -1n,
+  -10n,
+  -100n,
+  -1000n,
+  0.5,
+  Number.MIN_VALUE,
+  -Infinity,
 ];
 for (const firstDayOfWeek of invalidFirstDayOfWeekOptions) {
   assert.throws(RangeError, function() {
-    new Intl.Locale('en', {firstDayOfWeek});
+    new Intl.Locale("en", {firstDayOfWeek});
   }, `new Intl.Locale("en", {firstDayOfWeek: "${firstDayOfWeek}"}) throws RangeError`);
 }
diff --git a/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js b/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js
index 0c60306257c..723a822047d 100644
--- a/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js
+++ b/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js
@@ -9,15 +9,15 @@ info: |
     Intl.Locale( tag [, options] )
 
     ...
-    x. Let fw be ? GetOption(options, "firstDayOfWeek", "string", undefined, undefined).
-    x. If fw is not undefined, then
-       x. Set fw to !WeekdayToString(fw).
-       x. If fw does not match the type sequence (from UTS 35 Unicode Locale Identifier, section 3.2), throw a RangeError exception.
-    x. Set opt.[[fw]] to fw.
+    22. Let fw be ? GetOption(options, "firstDayOfWeek", string, empty, undefined).
+    23. If fw is not undefined, then
+       a. Set fw to WeekdayToUValue(fw).
+       b. If fw cannot be matched by the type Unicode locale nonterminal, throw a RangeError exception.
+    24. Set opt.[[fw]] to fw.
     ...
-    x. Let r be ! ApplyUnicodeExtensionToTag(tag, opt, relevantExtensionKeys).
+    35. Let r be MakeLocaleRecord(tag, opt, localeExtensionKeys).
     ...
-    x. Set locale.[[FirstDayOfWeek]] to r.[[fw]].
+    39. Set locale.[[FirstDayOfWeek]] to r.[[fw]].
     ...
 
 features: [Intl.Locale,Intl.Locale-info]
@@ -47,9 +47,25 @@ const validFirstDayOfWeekOptions = [
   [6, "en-u-fw-sat"],
   [7, "en-u-fw-sun"],
   [0, "en-u-fw-sun"],
+  [-0, "en-u-fw-sun"],
+  [100, "en-u-fw-100"],
+  [1000, "en-u-fw-1000"],
+  [1n, "en-u-fw-mon"],
+  [2n, "en-u-fw-tue"],
+  [3n, "en-u-fw-wed"],
+  [4n, "en-u-fw-thu"],
+  [5n, "en-u-fw-fri"],
+  [6n, "en-u-fw-sat"],
+  [7n, "en-u-fw-sun"],
+  [0n, "en-u-fw-sun"],
+  [100n, "en-u-fw-100"],
+  [1000n, "en-u-fw-1000"],
+  [NaN, "en-u-fw-nan"],
+  [Infinity, "en-u-fw-infinity"],
   [true, "en-u-fw"],
   [false, "en-u-fw-false"],
   [null, "en-u-fw-null"],
+  ["yes", "en-u-fw-yes"],
   ["primidi", "en-u-fw-primidi"],
   ["duodi", "en-u-fw-duodi"],
   ["tridi", "en-u-fw-tridi"],
@@ -68,13 +84,20 @@ const validFirstDayOfWeekOptions = [
 ];
 for (const [firstDayOfWeek, expected] of validFirstDayOfWeekOptions) {
   assert.sameValue(
-    new Intl.Locale('en', { firstDayOfWeek }).toString(),
+    new Intl.Locale("en", { firstDayOfWeek }).toString(),
     expected,
     `new Intl.Locale("en", { firstDayOfWeek: ${firstDayOfWeek} }).toString() returns "${expected}"`
   );
   assert.sameValue(
-    new Intl.Locale('en-u-fw-WED', { firstDayOfWeek }).toString(),
+    new Intl.Locale("en-u-fw-WED", { firstDayOfWeek }).toString(),
     expected,
     `new Intl.Locale("en-u-fw-WED", { firstDayOfWeek: ${firstDayOfWeek} }).toString() returns "${expected}"`
   );
+
+  let upperCase = String(firstDayOfWeek).toUpperCase();
+  assert.sameValue(
+    new Intl.Locale("en", { firstDayOfWeek: upperCase }).toString(),
+    expected,
+    `new Intl.Locale("en", { firstDayOfWeek: ${upperCase} }).toString() returns "${expected}"`
+  );
 }
diff --git a/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js b/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js
index d9aa88a33ba..0df2b4bea9b 100644
--- a/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js
+++ b/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js
@@ -4,7 +4,7 @@
 /*---
 esid: sec-intl.locale
 description: >
-    Checks valid cases for the options argument to the Locale constructor.
+    Checks valid cases for the locale argument to the Locale constructor.
 info: |
     Intl.Locale.prototype.firstDayOfWeek
     3. Return loc.[[FirstDayOfWeek]].
@@ -20,11 +20,29 @@ const validIds = [
   ["en-u-fw-fri", "fri"],
   ["en-u-fw-sat", "sat"],
   ["en-u-fw-sun", "sun"],
+
+  ["en-u-fw", ""],
+  ["en-u-fw-true", ""],
+  ["en-u-fw-false", "false"],
+  ["en-u-fw-yes", "yes"],
+  ["en-u-fw-lunedi", "lunedi"],
+  ["en-u-fw-montag", "montag"],
+
+  ["en-u-fw-000", "000"],
+  ["en-u-fw-001", "001"],
+  ["en-u-fw-11111111", "11111111"],
 ];
 for (const [id, expected] of validIds) {
   assert.sameValue(
     new Intl.Locale(id).firstDayOfWeek,
     expected,
-    `new Intl.Locale(${id}).firstDayOfWeek returns "${expected}"`
+    `new Intl.Locale("${id}").firstDayOfWeek returns "${expected}"`
+  );
+
+  let upperCase = id.toUpperCase();
+  assert.sameValue(
+    new Intl.Locale(upperCase).firstDayOfWeek,
+    expected,
+    `new Intl.Locale("${upperCase}").firstDayOfWeek returns "${expected}"`
   );
 }
diff --git a/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js b/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js
index bf6c8507cc5..5dd0ba2342f 100644
--- a/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js
+++ b/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js
@@ -36,16 +36,44 @@ const validFirstDayOfWeekOptions = [
   [6, "sat"],
   [7, "sun"],
   [0, "sun"],
+  [-0, "sun"],
+  [100, "100"],
+  [1000, "1000"],
+  [1n, "mon"],
+  [2n, "tue"],
+  [3n, "wed"],
+  [4n, "thu"],
+  [5n, "fri"],
+  [6n, "sat"],
+  [7n, "sun"],
+  [0n, "sun"],
+  [100n, "100"],
+  [1000n, "1000"],
+  [NaN, "nan"],
+  [Infinity, "infinity"],
+  [true, ""],
+  [false, "false"],
+  [null, "null"],
+  ["yes", "yes"],
+  ["lunedi", "lunedi"],
+  ["montag", "montag"],
 ];
 for (const [firstDayOfWeek, expected] of validFirstDayOfWeekOptions) {
   assert.sameValue(
-    new Intl.Locale('en', { firstDayOfWeek }).firstDayOfWeek,
+    new Intl.Locale("en", { firstDayOfWeek }).firstDayOfWeek,
     expected,
     `new Intl.Locale("en", { firstDayOfWeek: ${firstDayOfWeek} }).firstDayOfWeek returns "${expected}"`
   );
   assert.sameValue(
-    new Intl.Locale('en-u-fw-WED', { firstDayOfWeek }).firstDayOfWeek,
+    new Intl.Locale("en-u-fw-WED", { firstDayOfWeek }).firstDayOfWeek,
     expected,
     `new Intl.Locale("en-u-fw-WED", { firstDayOfWeek: ${firstDayOfWeek} }).firstDayOfWeek returns "${expected}"`
   );
+
+  let upperCase = String(firstDayOfWeek).toUpperCase();
+  assert.sameValue(
+    new Intl.Locale("en", { firstDayOfWeek: upperCase }).firstDayOfWeek,
+    expected,
+    `new Intl.Locale("en", { firstDayOfWeek: ${upperCase} }).firstDayOfWeek returns "${expected}"`
+  );
 }