Index: wp-admin/includes/screen.php
===================================================================
--- wp-admin/includes/screen.php	(revision 21928)
+++ wp-admin/includes/screen.php	(working copy)
@@ -475,10 +475,6 @@
 							$post_type = $post->post_type;
 					}
 					break;
-				case 'edit-tags' :
-					if ( null === $post_type && is_object_in_taxonomy( 'post', $taxonomy ? $taxonomy : 'post_tag' ) )
-						$post_type = 'post';
-					break;
 			}
  		}
 
@@ -494,6 +490,8 @@
 				$id .= '-' . $post_type;
 				break;
 			case 'edit-tags' :
+				if ( null === $post_type && is_object_in_taxonomy( 'post', $taxonomy ? $taxonomy : 'post_tag' ) )
+					$post_type = 'post';
 				if ( null === $taxonomy )
 					$taxonomy = 'post_tag';
 				$id = 'edit-' . $taxonomy;