diff --git a/wp-admin/includes/post.php b/wp-admin/includes/post.php
index 0287296a08..73a1a7261a 100644
--- a/wp-admin/includes/post.php
+++ b/wp-admin/includes/post.php
@@ -1279,15 +1279,24 @@ function wp_create_post_autosave( $post_id ) {
 		$new_autosave['ID'] = $old_autosave->ID;
 		$new_autosave['post_author'] = $post_author;
 
-		// Auto-save revisioned meta fields too.
+		// Auto-save revisioned meta fields.
 		foreach ( _wp_post_revision_meta_keys() as $meta_key ) {
-			if ( ! isset( $_POST[ $meta_key ] ) )
-				continue;
+			if ( isset( $_POST[ $meta_key ] ) && get_post_meta( $new_autosave['ID'], $meta_key, true ) != $_POST[ $meta_key ] ) {
+				// Use the underlying delete_metadata and add_metadata vs delete_post_meta
+				// and add_post_meta to make sure we're working with the actual revision meta.
+				delete_metadata( 'post', $new_autosave['ID'], $meta_key );
 
-			// Use the underlying delete_metadata and add_metadata vs delete_post_meta
-			// and add_post_meta to make sure we're working with the actual revision meta.
-			delete_metadata( 'post', $new_autosave['ID'], $meta_key );
-			add_metadata( 'post', $new_autosave['ID'], $meta_key, $_POST[ $meta_key ] );
+				if ( ! empty( $_POST[ $meta_key ] ) )
+					add_metadata( 'post', $new_autosave['ID'], $meta_key, $_POST[ $meta_key ] );
+			}
+		}
+
+		// Save the post format if different
+		if ( isset( $_POST['post_format'] ) && get_post_meta( $new_autosave['ID'], '_revision_post_format', true ) != $_POST['post_format'] ) {
+			delete_metadata( 'post', $new_autosave['ID'], '_revision_post_format' );
+
+			if ( ! empty( $_POST['post_format'] ) )
+				add_metadata( 'post', $new_autosave['ID'], '_revision_post_format', $_POST['post_format'] );
 		}
 
 		return wp_update_post( $new_autosave );
diff --git a/wp-includes/js/autosave.js b/wp-includes/js/autosave.js
index 6bab0e402e..566da2ddde 100644
--- a/wp-includes/js/autosave.js
+++ b/wp-includes/js/autosave.js
@@ -305,7 +305,7 @@ wp.autosave = wp.autosave || {};
 (function($){
 // Returns the data for saving in both localStorage and autosaves to the server
 wp.autosave.getPostData = function() {
-	var ed = typeof tinymce != 'undefined' ? tinymce.activeEditor : null, post_name, parent_id, cats = [],
+	var ed = typeof tinymce != 'undefined' ? tinymce.activeEditor : null, post_name, parent_id, post_format, cats = [],
 		data = {
 			action: 'autosave',
 			autosave: true,
@@ -364,6 +364,13 @@ wp.autosave.getPostData = function() {
 	if ( $('#auto_draft').val() == '1' )
 		data['auto_draft'] = '1';
 
+	post_format = $('#post_format').val() || '';
+	data['post_format'] = post_format == 'standard' ? '' : post_format;
+
+	$('.post-formats-fields').find('input[name^="_wp_format_"], textarea[name^="_wp_format_"]').each( function(i, field) {
+		data[ field.name ] = field.value || '';
+	});
+
 	return data;
 }
 
diff --git a/wp-includes/revision.php b/wp-includes/revision.php
index 0cddf445f6..5aa82f0b5b 100644
--- a/wp-includes/revision.php
+++ b/wp-includes/revision.php
@@ -134,12 +134,16 @@ function wp_save_post_revision( $post_id ) {
 
 			// Check whether revisioned meta fields have changed.
 			foreach ( _wp_post_revision_meta_keys() as $meta_key ) {
-				if ( get_post_meta( $post->ID, $meta_key ) != get_post_meta( $last_revision->ID, $meta_key ) ) {
+				if ( get_post_meta( $post->ID, $meta_key, true ) != get_post_meta( $last_revision->ID, $meta_key, true ) ) {
 					$post_has_changed = true;
 					break;
 				}
 			}
 
+			// Check whether the post format has changed
+			if ( get_post_format( $post->ID ) != get_post_meta( $last_revision->ID, '_revision_post_format', true ) )
+				$post_has_changed = true;
+
 			//don't save revision if post unchanged
 			if( ! $post_has_changed )
 				return;
@@ -280,16 +284,19 @@ function _wp_put_post_revision( $post = null, $autosave = false ) {
 
 	// Save revisioned meta fields.
 	foreach ( _wp_post_revision_meta_keys() as $meta_key ) {
-		$meta_values = get_post_meta( $post_id, $meta_key );
-		if ( false === $meta_values )
+		$meta_value = get_post_meta( $post_id, $meta_key, true );
+		if ( empty( $meta_value ) )
 			continue;
 
 		// Use the underlying add_metadata vs add_post_meta to make sure
 		// metadata is added to the revision post and not its parent.
-		foreach ( $meta_values as $meta_value )
-			add_metadata( 'post', $revision_id, $meta_key, $meta_value );
+		add_metadata( 'post', $revision_id, $meta_key, wp_slash( $meta_value ) );
 	}
 
+	// Save the post format
+	if ( $post_format = get_post_format( $post_id ) )
+		add_metadata( 'post', $revision_id, '_revision_post_format', $post_format );
+
 	return $revision_id;
 }
 
@@ -366,15 +373,16 @@ function wp_restore_post_revision( $revision_id, $fields = null ) {
 
 	// Restore revisioned meta fields.
 	foreach ( _wp_post_revision_meta_keys() as $meta_key ) {
-		delete_post_meta( $update['ID'], $meta_key );
-		$meta_values = get_post_meta( $revision['ID'], $meta_key );
-		if ( false === $meta_values )
-			continue;
-
-		foreach ( $meta_values as $meta_value )
-			add_post_meta( $update['ID'], $meta_key, $meta_value );
+		$meta_value = get_post_meta( $revision['ID'], $meta_key, true );
+		if ( empty( $meta_value ) )
+			$meta_value = '';
+		// Add slashes to data pulled from the db
+		update_post_meta( $update['ID'], $meta_key, wp_slash( $meta_value ) );
 	}
 
+	// Restore post format
+	set_post_format( $update['ID'], get_post_meta( $revision['ID'], '_revision_post_format', true ) );
+
 	$post_id = wp_update_post( $update );
 	if ( is_wp_error( $post_id ) )
 		return $post_id;
@@ -505,6 +513,7 @@ function _set_preview($post) {
 	$post->post_excerpt = $preview->post_excerpt;
 
 	add_filter( 'get_post_metadata', '_wp_preview_meta_filter', 10, 4 );
+	add_filter( 'get_the_terms', '_wp_preview_terms_filter', 10, 3 );
 
 	return $post;
 }
@@ -541,6 +550,29 @@ function _wp_preview_meta_filter( $value, $object_id, $meta_key, $single ) {
 	return get_post_meta( $preview->ID, $meta_key, $single );
 }
 
+/**
+ * Filters terms lookup to get the post format saved with the preview revision.
+ *
+ * @since 2.6
+ * @access private
+ */
+function _wp_preview_terms_filter( $terms, $post_id, $taxonomy ) {
+	$post = get_post();
+
+	if ( $post->ID != $post_id || 'post_format' != $taxonomy || 'revision' == $post->post_type )
+		return $terms;
+
+	if ( ! $preview = wp_get_post_autosave( $post->ID ) )
+		return $terms;
+
+	if ( $post_format = get_post_meta( $preview->ID, '_revision_post_format', true ) ) {
+		if ( $term = get_term_by( 'slug', 'post-format-' . sanitize_key( $post_format ), 'post_format' ) )
+			$terms = array( $term ); // Can only have one post format
+	}
+
+	return $terms;
+}
+
 function _wp_get_post_revision_version( $revision ) {
 	if ( is_object( $revision ) )
 		$revision = get_object_vars( $revision );