Ticket #16021: 16021.patch

wp-admin/update-core.php

@@ -74 +74 @@
         echo '</p>';
         if ( 'en_US' != $update->locale && ( !isset($wp_local_package) || $wp_local_package != $update->locale ) )
             echo '<p class="hint">'.__('This localized version contains both the translation and various other localization fixes. You can skip upgrading if you want to keep your current translation.').'</p>';
-        else if ( 'en_US' == $update->locale && get_locale() != 'en_US' ) {
+        else if ( 'en_US' == $update->locale && get_locale() != 'en_US' && 'development' != $update->response ) {
             echo '<p class="hint">'.sprintf( __('You are about to install WordPress %s <strong>in English (US).</strong> There is a chance this update will break your translation. You may prefer to wait for the localized version to be released.'), $update->current ).'</p>';
         }
         echo '</form>';