diff --git a/src/common/bcp47.cpp b/src/common/bcp47.cpp
index 67d185ba5..4c0cdd2cd 100644
--- a/src/common/bcp47.cpp
+++ b/src/common/bcp47.cpp
@@ -323,8 +323,6 @@ language_c::parse_extensions(std::string const &str) {
     else
       m_extensions.back().extensions.emplace_back(part);
 
-  std::sort(m_extensions.begin(), m_extensions.end());
-
   return validate_extensions();
 }
 
@@ -640,9 +638,7 @@ language_c::add_extension(extension_t const &extension) {
   for (auto const &extension_subtag : extension.extensions)
     extensions_lower.emplace_back(mtx::string::to_lower_ascii(extension_subtag));
 
-  auto cleaned_extension = extension_t{ mtx::string::to_lower_ascii(extension.identifier), extensions_lower };
-  m_extensions.insert(std::lower_bound(m_extensions.begin(), m_extensions.end(), cleaned_extension), cleaned_extension);
-
+  m_extensions.emplace_back(mtx::string::to_lower_ascii(extension.identifier), extensions_lower);
   m_formatted_up_to_date = false;
 
   return *this;
@@ -851,6 +847,8 @@ language_c &
 language_c::to_canonical_form() {
   m_formatted_up_to_date = false;
 
+  std::sort(m_extensions.begin(), m_extensions.end());
+
   return canonicalize_preferred_values();
 }
 
diff --git a/tests/unit/common/bcp47.cpp b/tests/unit/common/bcp47.cpp
index 19f382a43..d0d060b70 100644
--- a/tests/unit/common/bcp47.cpp
+++ b/tests/unit/common/bcp47.cpp
@@ -91,6 +91,18 @@ TEST(BCP47LanguageTags, Formatting) {
   l.set_valid(true);
 
   EXPECT_EQ("ja-t-test-u-attr-co-phonebk-attr-zz-oooqqq"s, l.format());
+
+  l = language_c{};
+  l.set_language("ja");
+  l.add_extension({ "u"s, { "attr"s, "co"s, "phonebk"s, "attr"s, "zz"s, "oooqqq"s }});
+  l.add_extension({ "t"s, { "test"s }});
+  l.set_valid(true);
+
+  EXPECT_EQ("ja-u-attr-co-phonebk-attr-zz-oooqqq-t-test"s, l.format());
+
+  l.to_canonical_form();
+
+  EXPECT_EQ("ja-t-test-u-attr-co-phonebk-attr-zz-oooqqq"s, l.format());
 }
 
 TEST(BCP47LanguageTags, FormattingInvalidWithoutLanguage) {
@@ -319,7 +331,7 @@ TEST(BCP47LanguageTags, ExtensionsRFC6497) {
 
 TEST(BCP47LanguageTags, ExtensionsFormatting) {
   EXPECT_EQ("ja-t-test-u-attr-co-phonebk"s, language_c::parse("ja-T-Test-U-AttR-CO-phoNEbk").format());
-  EXPECT_EQ("ja-t-test-u-attr-co-phonebk"s, language_c::parse("ja-U-AttR-CO-phoNEbk-T-Test").format());
+  EXPECT_EQ("ja-u-attr-co-phonebk-t-test"s, language_c::parse("ja-U-AttR-CO-phoNEbk-T-Test").format());
 }
 
 TEST(BCP47LanguageTags, Matching) {