diff --git a/wp-includes/l10n.php b/wp-includes/l10n.php
index 1a0474f465..b7d9d24af0 100644
--- a/wp-includes/l10n.php
+++ b/wp-includes/l10n.php
@@ -138,7 +138,7 @@ function determine_locale() {
 		$determined_locale = get_user_locale();
 	}
 
-	if ( ! empty( $_GET['wp_lang'] ) && 'wp-login.php' === $GLOBALS['pagenow'] ) {
+	if ( ! empty( $_GET['wp_lang'] ) && ! empty( $GLOBALS['pagenow'] ) && 'wp-login.php' === $GLOBALS['pagenow'] ) {
 		$determined_locale = sanitize_text_field( $_GET['wp_lang'] );
 	}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 6a25caa58d..fc875dbc0b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44316';
+$wp_version = '5.1-alpha-44317';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.