diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 270fcc7283382..40ae2f045d7bf 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -1358,7 +1358,7 @@ function block_core_navigation_get_most_recently_published_navigation() {
  * @param WP_Post $post         `wp_navigation` post object corresponding to the block.
  * @return string Serialized inner blocks in mock Navigation block wrapper, with hooked blocks inserted, if any.
  */
-function block_core_navigation_insert_hooked_blocks( $inner_blocks, $post = null ) {
+function block_core_navigation_insert_hooked_blocks( $inner_blocks, $post ) {
 	$before_block_visitor = null;
 	$after_block_visitor  = null;
 	$hooked_blocks        = get_hooked_blocks();