Index: trunk/wp-admin/includes/class-wp-upgrader.php
===================================================================
--- trunk/wp-admin/includes/class-wp-upgrader.php
+++ trunk/wp-admin/includes/class-wp-upgrader.php
@@ -152,7 +152,7 @@
 		}
 
 		//We need a working directory
-		$working_dir = $upgrade_folder . basename($package, '.zip');
+		$working_dir = $upgrade_folder . substr(basename($package, '.zip'), 0, 32);
 
 		// Clean up working directory
 		if ( $wp_filesystem->is_dir($working_dir) )