diff --git a/ecmascript/intl/locale_helper.cpp b/ecmascript/intl/locale_helper.cpp
index fed096cf2e5fcee58a876ecebdd11addecb8dc09..477af394e115130cd451bff66c5a8ff415fa65c1 100644
--- a/ecmascript/intl/locale_helper.cpp
+++ b/ecmascript/intl/locale_helper.cpp
@@ -258,7 +258,6 @@ bool LocaleHelper::IsStructurallyValidLanguageTag(const JSHandle<EcmaString> &ta
     std::string tagCollection = ConvertToStdString(tag);
     std::vector<std::string> containers;
     std::string substring;
-    std::set<std::string> uniqueSubtags;
     size_t address = 1;
     for (auto it = tagCollection.begin(); it != tagCollection.end(); it++) {
         if (*it != '-' && it != tagCollection.end() - 1) {
@@ -270,7 +269,8 @@ bool LocaleHelper::IsStructurallyValidLanguageTag(const JSHandle<EcmaString> &ta
             containers.push_back(substring);
             if (IsVariantSubtag(substring)) {
                 std::transform(substring.begin(), substring.end(), substring.begin(), AsciiAlphaToLower);
-                if (!uniqueSubtags.insert(substring).second) {
+                // Ignore the first tag when checking for duplicate subtags.
+                if (std::count(containers.begin(), containers.end(), substring) > 2) {
                     return false;
                 }
             }