diff --git a/src/wp-includes/nav-menu.php b/src/wp-includes/nav-menu.php
index 9b6eeba..2886095 100644
--- a/src/wp-includes/nav-menu.php
+++ b/src/wp-includes/nav-menu.php
@@ -92,6 +92,14 @@ function register_nav_menus( $locations = array() ) {
 
 	add_theme_support( 'menus' );
 
+	foreach ( $locations as $key => $value ) {
+		if ( is_int( $key ) ) {
+			/* translators: %s: menu location value */
+			$message = sprintf( __( 'Menu location slug (key) for menu "%s" should not be a int.' ), $value );
+			_doing_it_wrong( __FUNCTION__, $message, '5.2' );
+		}
+	}
+
 	$_wp_registered_nav_menus = array_merge( (array) $_wp_registered_nav_menus, $locations );
 }