diff --git a/applications/services/language.php b/applications/services/language.php
diff --git a/extensions/languages/en-GB/manifest.xml b/extensions/languages/en-GB/manifest.xml
@@ -16,6 +16,6 @@
         <locale>en_GB.utf8, en_GB.UTF-8, en_GB, eng_GB, en, english, english-uk, uk, gbr, britain, england, great
             britain, uk, united kingdom, united-kingdom
         </locale>
-        <firstDay>0</firstDay>
+        <first_day>0</first_day>
     </metadata>
 </extension>