diff --git src/wp-includes/capabilities-functions.php src/wp-includes/capabilities-functions.php
index 4274fa5..e0c07a4 100644
--- src/wp-includes/capabilities-functions.php
+++ src/wp-includes/capabilities-functions.php
@@ -52,6 +52,10 @@ function map_meta_cap( $cap, $user_id ) {
 		}
 
 		$post_type = get_post_type_object( $post->post_type );
+		if ( ! $post_type ) {
+			$cap = 'edit_others_posts';
+			break;
+		}
 
 		if ( ! $post_type->map_meta_cap ) {
 			$caps[] = $post_type->cap->$cap;
@@ -100,6 +104,10 @@ function map_meta_cap( $cap, $user_id ) {
 		}
 
 		$post_type = get_post_type_object( $post->post_type );
+		if ( ! $post_type ) {
+			$cap = 'edit_others_posts';
+			break;
+		}
 
 		if ( ! $post_type->map_meta_cap ) {
 			$caps[] = $post_type->cap->$cap;
@@ -142,6 +150,10 @@ function map_meta_cap( $cap, $user_id ) {
 		}
 
 		$post_type = get_post_type_object( $post->post_type );
+		if ( ! $post_type ) {
+			$cap = 'edit_others_posts';
+			break;
+		}
 
 		if ( ! $post_type->map_meta_cap ) {
 			$caps[] = $post_type->cap->$cap;
@@ -168,6 +180,10 @@ function map_meta_cap( $cap, $user_id ) {
 	case 'publish_post':
 		$post = get_post( $args[0] );
 		$post_type = get_post_type_object( $post->post_type );
+		if ( ! $post_type ) {
+			$cap = 'edit_others_posts';
+			break;
+		}
 
 		$caps[] = $post_type->cap->publish_posts;
 		break;