diff --git a/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js b/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js
index a2a754d923..727134d7f9 100644
--- a/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js
+++ b/test/intl402/Locale/constructor-options-firstDayOfWeek-invalid.js
@@ -9,7 +9,10 @@ info: |
     Intl.Locale( tag [, options] )
 
     ...
-    x. Let numberingSystem be ? GetOption(options, "firstDayOfWeek", "string", < *"mon"*, *"tue"*, *"wed"*, *"thu"*, *"fri"*, *"sat"*, *"sun"*, *"0"*, *"1"*, *"2"*, *"3"*, *"4"*, *"5"*, *"6"*, *"7"*> , undefined).
+    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.
     ...
 
 features: [Intl.Locale,Intl.Locale-info]
@@ -19,10 +22,7 @@ const invalidFirstDayOfWeekOptions = [
   "",
   "m",
   "mo",
-  "monday",
-  true,
-  false,
-  null,
+  "longerThan8Chars",
 ];
 for (const firstDayOfWeek of invalidFirstDayOfWeekOptions) {
   assert.throws(RangeError, function() {
diff --git a/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js b/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js
index d9efe8bf82..4905bfc0c8 100644
--- a/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js
+++ b/test/intl402/Locale/constructor-options-firstDayOfWeek-valid.js
@@ -9,18 +9,15 @@ info: |
     Intl.Locale( tag [, options] )
 
     ...
-    x. Let numberingSystem be ? GetOption(options, "firstDayOfWeek", "string", < *"mon"*, *"tue"*, *"wed"*, *"thu"*, *"fri"*, *"sat"*, *"sun"*, *"0"*, *"1"*, *"2"*, *"3"*, *"4"*, *"5"*, *"6"*, *"7"*> , undefined).
-    x. Let firstDay be *undefined*.
-    x. If fw is not *undefined*, then
-       x. Set firstDay to !WeekdayToString(fw).
-       x. Set opt.[[fw]] to firstDay.
+    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.
     ...
     x. Let r be ! ApplyUnicodeExtensionToTag(tag, opt, relevantExtensionKeys).
     ...
-    x. Let firstDay be *undefined*.
-    x. If r.[[fw]] is not *undefined*, then
-       x. Set firstDay to ! WeekdayToNumber(r.[[fw]]).
-       x. Set locale.[[FirstDayOfWeek]] to firstDay.
+    x. Set locale.[[FirstDayOfWeek]] to r.[[fw]].
     ...
 
 features: [Intl.Locale,Intl.Locale-info]
@@ -50,6 +47,24 @@ const validFirstDayOfWeekOptions = [
   [6, "en-u-fw-sat"],
   [7, "en-u-fw-sun"],
   [0, "en-u-fw-sun"],
+  [true, "en-u-fw-true"],
+  [false, "en-u-fw-false"],
+  [null, "en-u-fw-null"],
+  ["primidi", "en-u-fw-primidi"],
+  ["duodi", "en-u-fw-duodi"],
+  ["tridi", "en-u-fw-tridi"],
+  ["quartidi", "en-u-fw-quartidi"],
+  ["quintidi", "en-u-fw-quintidi"],
+  ["sextidi", "en-u-fw-sextidi"],
+  ["septidi", "en-u-fw-septidi"],
+  ["octidi", "en-u-fw-octidi"],
+  ["nonidi", "en-u-fw-nonidi"],
+  ["decadi", "en-u-fw-decadi"],
+  ["frank", "en-u-fw-frank"],
+  ["yungfong", "en-u-fw-yungfong"],
+  ["yung-fong", "en-u-fw-yung-fong"],
+  ["tang", "en-u-fw-tang"],
+  ["frank-yung-fong-tang", "en-u-fw-frank-yung-fong-tang"],
 ];
 for (const [firstDayOfWeek, expected] of validFirstDayOfWeekOptions) {
   assert.sameValue(
diff --git a/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js b/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js
index 12acd526a9..d9aa88a33b 100644
--- a/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js
+++ b/test/intl402/Locale/prototype/firstDayOfWeek/valid-id.js
@@ -13,13 +13,13 @@ features: [Intl.Locale,Intl.Locale-info]
 ---*/
 
 const validIds = [
-  ["en-u-fw-mon", 1],
-  ["en-u-fw-tue", 2],
-  ["en-u-fw-wed", 3],
-  ["en-u-fw-thu", 4],
-  ["en-u-fw-fri", 5],
-  ["en-u-fw-sat", 6],
-  ["en-u-fw-sun", 7],
+  ["en-u-fw-mon", "mon"],
+  ["en-u-fw-tue", "tue"],
+  ["en-u-fw-wed", "wed"],
+  ["en-u-fw-thu", "thu"],
+  ["en-u-fw-fri", "fri"],
+  ["en-u-fw-sat", "sat"],
+  ["en-u-fw-sun", "sun"],
 ];
 for (const [id, expected] of validIds) {
   assert.sameValue(
diff --git a/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js b/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js
index 6f1643afd2..bf6c8507cc 100644
--- a/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js
+++ b/test/intl402/Locale/prototype/firstDayOfWeek/valid-options.js
@@ -13,29 +13,29 @@ features: [Intl.Locale,Intl.Locale-info]
 ---*/
 
 const validFirstDayOfWeekOptions = [
-  ["mon", 1],
-  ["tue", 2],
-  ["wed", 3],
-  ["thu", 4],
-  ["fri", 5],
-  ["sat", 6],
-  ["sun", 7],
-  ["1", 1],
-  ["2", 2],
-  ["3", 3],
-  ["4", 4],
-  ["5", 5],
-  ["6", 6],
-  ["7", 7],
-  ["0", 7],
-  [1, 1],
-  [2, 2],
-  [3, 3],
-  [4, 4],
-  [5, 5],
-  [6, 6],
-  [7, 7],
-  [0, 7],
+  ["mon", "mon"],
+  ["tue", "tue"],
+  ["wed", "wed"],
+  ["thu", "thu"],
+  ["fri", "fri"],
+  ["sat", "sat"],
+  ["sun", "sun"],
+  ["1", "mon"],
+  ["2", "tue"],
+  ["3", "wed"],
+  ["4", "thu"],
+  ["5", "fri"],
+  ["6", "sat"],
+  ["7", "sun"],
+  ["0", "sun"],
+  [1, "mon"],
+  [2, "tue"],
+  [3, "wed"],
+  [4, "thu"],
+  [5, "fri"],
+  [6, "sat"],
+  [7, "sun"],
+  [0, "sun"],
 ];
 for (const [firstDayOfWeek, expected] of validFirstDayOfWeekOptions) {
   assert.sameValue(