Index: class-wp-upgrader.php
===================================================================
--- class-wp-upgrader.php	(revision 22659)
+++ class-wp-upgrader.php	(working copy)
@@ -92,8 +92,8 @@
 					if ( ! $wp_filesystem->wp_plugins_dir() )
 						return new WP_Error('fs_no_plugins_dir', $this->strings['fs_no_plugins_dir']);
 					break;
-				case WP_CONTENT_DIR . '/themes':
-					if ( ! $wp_filesystem->find_folder(WP_CONTENT_DIR . '/themes') )
+				case get_theme_root():
+					if ( ! $wp_filesystem->find_folder( get_theme_root() ) )
 						return new WP_Error('fs_no_themes_dir', $this->strings['fs_no_themes_dir']);
 					break;
 				default:
@@ -207,7 +207,7 @@
 			$source_files = array_keys( $wp_filesystem->dirlist($source) );
 
 		//Protection against deleting files in any important base directories.
-		if ( in_array( $destination, array(ABSPATH, WP_CONTENT_DIR, WP_PLUGIN_DIR, WP_CONTENT_DIR . '/themes') ) ) {
+		if ( in_array( $destination, array(ABSPATH, WP_CONTENT_DIR, WP_PLUGIN_DIR, get_theme_root()) ) ) {
 			$remote_destination = trailingslashit($remote_destination) . trailingslashit(basename($source));
 			$destination = trailingslashit($destination) . trailingslashit(basename($source));
 		}
@@ -715,7 +715,7 @@
 		// Install the parent theme
 		$parent_result = $this->run( array(
 			'package' => $api->download_link,
-			'destination' => WP_CONTENT_DIR . '/themes',
+			'destination' => get_theme_root(),
 			'clear_destination' => false, //Do not overwrite files.
 			'clear_working' => true
 		) );
@@ -749,7 +749,7 @@
 
 		$options = array(
 						'package' => $package,
-						'destination' => WP_CONTENT_DIR . '/themes',
+						'destination' => get_theme_root(),
 						'clear_destination' => false, //Do not overwrite files.
 						'clear_working' => true
 						);
@@ -791,7 +791,7 @@
 
 		$options = array(
 						'package' => $r['package'],
-						'destination' => WP_CONTENT_DIR . '/themes',
+						'destination' => get_theme_root(),
 						'clear_destination' => true,
 						'clear_working' => true,
 						'hook_extra' => array(
@@ -867,7 +867,7 @@
 
 			$options = array(
 							'package' => $r['package'],
-							'destination' => WP_CONTENT_DIR . '/themes',
+							'destination' => get_theme_root(),
 							'clear_destination' => true,
 							'clear_working' => true,
 							'hook_extra' => array(
@@ -989,7 +989,7 @@
 			else
 				return false;
 		}
-		return wp_get_theme( $theme, WP_CONTENT_DIR . '/themes/' );
+		return wp_get_theme( $theme, get_theme_root() . '/' );
 	}
 
 }