diff --git a/wp-admin/includes/post.php b/wp-admin/includes/post.php
index 31e1a1559e..48caefa4d9 100644
--- a/wp-admin/includes/post.php
+++ b/wp-admin/includes/post.php
@@ -683,7 +683,7 @@ function get_default_post_to_edit( $post_type = 'post', $create_in_db = false )
 	 * @param string  $post_content Default post content.
 	 * @param WP_Post $post         Post object.
 	 */
-	$post->post_content = apply_filters( 'default_content', $post_content, $post );
+	$post->post_content = (string) apply_filters( 'default_content', $post_content, $post );
 
 	/**
 	 * Filters the default post title initially used in the "Write Post" form.
@@ -693,7 +693,7 @@ function get_default_post_to_edit( $post_type = 'post', $create_in_db = false )
 	 * @param string  $post_title Default post title.
 	 * @param WP_Post $post       Post object.
 	 */
-	$post->post_title = apply_filters( 'default_title', $post_title, $post );
+	$post->post_title = (string) apply_filters( 'default_title', $post_title, $post );
 
 	/**
 	 * Filters the default post excerpt initially used in the "Write Post" form.
@@ -703,7 +703,7 @@ function get_default_post_to_edit( $post_type = 'post', $create_in_db = false )
 	 * @param string  $post_excerpt Default post excerpt.
 	 * @param WP_Post $post         Post object.
 	 */
-	$post->post_excerpt = apply_filters( 'default_excerpt', $post_excerpt, $post );
+	$post->post_excerpt = (string) apply_filters( 'default_excerpt', $post_excerpt, $post );
 
 	return $post;
 }
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 212d406a9e..85eff0a362 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44223';
+$wp_version = '5.1-alpha-44224';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.