Index: plugin.php
===================================================================
--- plugin.php	(revision 27070)
+++ plugin.php	(working copy)
@@ -920,7 +920,9 @@
 		}
 		unset($uninstallable_plugins);
 
-		define('WP_UNINSTALL_PLUGIN', $file);
+		if ( ! defined( 'WP_UNINSTALL_PLUGIN' ) )
+			define('WP_UNINSTALL_PLUGIN', $file);
+
 		include WP_PLUGIN_DIR . '/' . dirname($file) . '/uninstall.php';
 
 		return true;