diff --git src/wp-admin/includes/class-wp-screen.php src/wp-admin/includes/class-wp-screen.php
index a7d9a1a..f4e67c9 100644
--- src/wp-admin/includes/class-wp-screen.php
+++ src/wp-admin/includes/class-wp-screen.php
@@ -308,6 +308,9 @@ final class WP_Screen {
 					if ( null === $post_type && is_object_in_taxonomy( 'post', $taxonomy ? $taxonomy : 'post_tag' ) )
 						$post_type = 'post';
 					break;
+				case 'upload':
+					$post_type = 'attachment';
+					break;
 			}
 		}
 
diff --git tests/phpunit/tests/admin/includesScreen.php tests/phpunit/tests/admin/includesScreen.php
index f60e0b8..c721135 100644
--- tests/phpunit/tests/admin/includesScreen.php
+++ tests/phpunit/tests/admin/includesScreen.php
@@ -12,7 +12,7 @@ class Tests_Admin_includesScreen extends WP_UnitTestCase {
 		'edit-tags.php' => array( 'base' => 'edit-tags', 'id' => 'edit-post_tag', 'post_type' => 'post', 'taxonomy' => 'post_tag' ),
 		'edit-tags.php?taxonomy=post_tag' => array( 'base' => 'edit-tags', 'id' => 'edit-post_tag', 'post_type' => 'post', 'taxonomy' => 'post_tag' ),
 		'edit-tags.php?taxonomy=category' => array( 'base' => 'edit-tags', 'id' => 'edit-category', 'post_type' => 'post', 'taxonomy' => 'category' ),
-		'upload.php' => array( 'base' => 'upload', 'id' => 'upload' ),
+		'upload.php' => array( 'base' => 'upload', 'id' => 'upload', 'post_type' => 'attachment' ),
 		'media-new.php' => array( 'action' => 'add', 'base' => 'media', 'id' => 'media' ),
 		'edit.php?post_type=page' => array( 'base' => 'edit', 'id' => 'edit-page', 'post_type' => 'page' ),
 		'link-manager.php' => array( 'base' => 'link-manager', 'id' => 'link-manager' ),