--- a/js/src/builtin/Intl.js
+++ b/js/src/builtin/Intl.js
@@ -102,21 +102,21 @@ function removeUnicodeExtensions(locale)
     // the concatenation.
     var pos = callFunction(std_String_indexOf, locale, "-x-");
     if (pos < 0)
         pos = locale.length;
 
     var left = callFunction(String_substring, locale, 0, pos);
     var right = callFunction(String_substring, locale, pos);
 
-    var extensions;
     var unicodeLocaleExtensionSequenceRE = getUnicodeLocaleExtensionSequenceRE();
-    while ((extensions = regexp_exec_no_statics(unicodeLocaleExtensionSequenceRE, left)) !== null) {
-        left = StringReplaceString(left, extensions[0], "");
-        unicodeLocaleExtensionSequenceRE.lastIndex = 0;
+    var extensions = regexp_exec_no_statics(unicodeLocaleExtensionSequenceRE, left);
+    if (extensions !== null) {
+        left = callFunction(String_substring, left, 0, extensions.index) +
+               callFunction(String_substring, left, extensions.index + extensions[0].length);
     }
 
     var combined = left + right;
     assert(IsStructurallyValidLanguageTag(combined), "recombination produced an invalid language tag");
     assert(function() {
         var uindex = callFunction(std_String_indexOf, combined, "-u-");
         if (uindex < 0)
             return true;