Index: src/wp-includes/post.php
===================================================================
--- src/wp-includes/post.php	(revision 41324)
+++ src/wp-includes/post.php	(working copy)
@@ -1710,12 +1710,18 @@
  */
 function add_post_meta( $post_id, $meta_key, $meta_value, $unique = false ) {
 	// Make sure meta is added to the post, not a revision.
-	if ( $the_post = wp_is_post_revision($post_id) )
+	if ( $the_post = wp_is_post_revision( $post_id ) ) {
 		$post_id = $the_post;
+	}
 
-	return add_metadata('post', $post_id, $meta_key, $meta_value, $unique);
-}
+	$added = add_metadata( 'post', $post_id, $meta_key, $meta_value, $unique );
+
+	if ( $added ) {
+		wp_cache_set( 'last_changed', microtime(), 'posts' );
+	}
 
+	return $added;
+}
 /**
  * Remove metadata matching criteria from a post.
  *
@@ -1733,10 +1739,17 @@
  */
 function delete_post_meta( $post_id, $meta_key, $meta_value = '' ) {
 	// Make sure meta is added to the post, not a revision.
-	if ( $the_post = wp_is_post_revision($post_id) )
+	if ( $the_post = wp_is_post_revision( $post_id ) ) {
 		$post_id = $the_post;
+	}
+
+	$deleted = delete_metadata( 'post', $post_id, $meta_key, $meta_value );
+
+	if ( $deleted ) {
+		wp_cache_set( 'last_changed', microtime(), 'posts' );
+	}
 
-	return delete_metadata('post', $post_id, $meta_key, $meta_value);
+	return $deleted;
 }
 
 /**
@@ -1775,10 +1788,17 @@
  */
 function update_post_meta( $post_id, $meta_key, $meta_value, $prev_value = '' ) {
 	// Make sure meta is added to the post, not a revision.
-	if ( $the_post = wp_is_post_revision($post_id) )
+	if ( $the_post = wp_is_post_revision( $post_id ) ) {
 		$post_id = $the_post;
+	}
 
-	return update_metadata('post', $post_id, $meta_key, $meta_value, $prev_value);
+	$updated = update_metadata( 'post', $post_id, $meta_key, $meta_value, $prev_value );
+
+	if ( $updated ) {
+		wp_cache_set( 'last_changed', microtime(), 'posts' );
+	}
+
+	return $updated;
 }
 
 /**
@@ -1790,7 +1810,13 @@
  * @return bool Whether the post meta key was deleted from the database.
  */
 function delete_post_meta_by_key( $post_meta_key ) {
-	return delete_metadata( 'post', null, $post_meta_key, '', true );
+	$deleted = delete_metadata( 'post', null, $post_meta_key, '', true );
+
+	if ( $deleted ) {
+		wp_cache_set( 'last_changed', microtime(), 'posts' );
+	}
+
+	return $deleted;
 }
 
 /**