Index: wp-admin/includes/revision.php
===================================================================
--- wp-admin/includes/revision.php	(revision 24859)
+++ wp-admin/includes/revision.php	(working copy)
@@ -179,8 +179,11 @@ function wp_prepare_revisions_for_js( $post, $selected_revision_id, $from = null
 	// Now, grab the initial diff
 	$compare_two_mode = is_numeric( $from );
 	if ( ! $compare_two_mode ) {
-		$from = array_keys( array_slice( $revisions, array_search( $selected_revision_id, array_keys( $revisions ) ) - 1, 1, true ) );
-		$from = $from[0];
+		$found = array_search( $selected_revision_id, array_keys( $revisions ) );
+		if ( $found )
+			$from = array_shift( array_keys( array_slice( $revisions, $found - 1, 1, true ) ) );
+		else
+			$from = 0;
 	}
 
 	$from = absint( $from );
Index: wp-admin/js/revisions.js
===================================================================
--- wp-admin/js/revisions.js	(revision 24859)
+++ wp-admin/js/revisions.js	(working copy)
@@ -155,8 +155,6 @@ window.wp = window.wp || {};
 			this.listenTo( this.slider, 'hovered:revision', this.updateRevision );
 			this.listenTo( this.slider, 'change:hovering', this.setHovering );
 			this.listenTo( this.slider, 'change:scrubbing', this.setScrubbing );
-
-			this.set({ revision: this.revisions.get( this.frame.get('to') ) });
 		},
 
 
@@ -754,9 +752,12 @@ window.wp = window.wp || {};
 		},
 
 		prepare: function() {
-			return _.extend( { type: 'tooltip' }, {
-				attributes: this.model.get('revision').toJSON()
-			});
+			if ( _.isNull( this.model.get('revision') ) )
+				return;
+			else
+				return _.extend( { type: 'tooltip' }, {
+					attributes: this.model.get('revision').toJSON()
+				});
 		},
 
 		render: function() {