Index: wp-admin/includes/revision.php
===================================================================
--- wp-admin/includes/revision.php	(revision 24856)
+++ wp-admin/includes/revision.php	(working copy)
@@ -179,6 +179,7 @@
 	// Now, grab the initial diff
 	$compare_two_mode = is_numeric( $from );
 	if ( ! $compare_two_mode ) {
+		// Old call works for first revision ~ $from = array_reverse( array_keys( array_slice( $revisions, array_search( $selected_revision_id, array_keys( $revisions ) ), 2, true ) ) );
 		$from = array_keys( array_slice( $revisions, array_search( $selected_revision_id, array_keys( $revisions ) ) - 1, 1, true ) );
 		$from = $from[0];
 	}
Index: wp-admin/js/revisions.js
===================================================================
--- wp-admin/js/revisions.js	(revision 24856)
+++ wp-admin/js/revisions.js	(working copy)
@@ -656,6 +656,8 @@
 			_(tickCount).times( function( index ){
 				this.$el.append( '<div style="' + this.direction + ': ' + ( 100 * tickWidth * index ) + '%"></div>' );
 			}, this );
+
+			this.reportTickPosition();
 		}
 	});