Index: wp-admin/includes/post.php
===================================================================
--- wp-admin/includes/post.php	(revision 23797)
+++ wp-admin/includes/post.php	(working copy)
@@ -1267,20 +1267,41 @@
  * @return unknown
  */
 function wp_create_post_autosave( $post_id ) {
+	if ( ! $post = get_post( $post_id ) )
+		return;
+
 	$translated = _wp_translate_postdata( true );
 	if ( is_wp_error( $translated ) )
 		return $translated;
 
 	$post_author = get_current_user_id();
+	$new_data = $_POST;
 
 	// Store one autosave per author. If there is already an autosave, overwrite it.
 	if ( $old_autosave = wp_get_post_autosave( $post_id, $post_author ) ) {
 		$new_autosave = _wp_post_revision_fields( $_POST, true );
 		$new_autosave['ID'] = $old_autosave->ID;
 		$new_autosave['post_author'] = $post_author;
-		return wp_update_post( $new_autosave );
+
+		$new_data = $new_autosave;
 	}
 
+	if ( apply_filters( 'wp_save_post_revision_check_for_changes', true, $post, $new_data ) && is_array( $new_data ) ) {
+		$post_has_changed = false;
+		foreach ( array_keys( _wp_post_revision_fields() ) as $field ) {
+			if ( normalize_whitespace( $new_data[ $field ] ) != normalize_whitespace( $post[ $field ] ) ) {
+				$post_has_changed = true;
+				break;
+			}
+		}
+		//don't save revision if post unchanged
+		if( ! $post_has_changed )
+			return;
+	}
+
+	if ( isset( $new_autosave ) )
+		return wp_update_post( $new_autosave );
+
 	// _wp_put_post_revision() expects unescaped.
 	$_POST = wp_unslash($_POST);