diff --git a/wp-includes/blocks.php b/wp-includes/blocks.php
index 0e6b6a63f4..2eec688b75 100644
--- a/wp-includes/blocks.php
+++ b/wp-includes/blocks.php
@@ -685,7 +685,7 @@ function render_block( $parsed_block ) {
 
 	$context = array();
 
-	if ( ! empty( $post ) ) {
+	if ( $post instanceof WP_Post ) {
 		$context['postId'] = $post->ID;
 
 		/*
@@ -697,7 +697,7 @@ function render_block( $parsed_block ) {
 		$context['postType'] = $post->post_type;
 	}
 
-	if ( isset( $wp_query->tax_query->queried_terms['category'] ) ) {
+	if ( $wp_query instanceof WP_Query && isset( $wp_query->tax_query->queried_terms['category'] ) ) {
 		$context['query'] = array( 'categoryIds' => array() );
 		foreach ( $wp_query->tax_query->queried_terms['category']['terms'] as $category_slug_or_id ) {
 			$context['query']['categoryIds'][] = 'slug' === $wp_query->tax_query->queried_terms['category']['field'] ? get_cat_ID( $category_slug_or_id ) : $category_slug_or_id;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index e3fd9af6a1..552839a799 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-48242';
+$wp_version = '5.5-alpha-48243';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.