diff --git a/src/compositor/meta-plugin-manager.c b/src/compositor/meta-plugin-manager.c
index 834f678dd..9f6e67273 100644
--- a/src/compositor/meta-plugin-manager.c
+++ b/src/compositor/meta-plugin-manager.c
@@ -153,10 +153,17 @@ meta_plugin_manager_event_simple (MetaPluginManager *plugin_mgr,
                                   MetaWindowActor   *actor,
                                   MetaPluginEffect   event)
 {
-  MetaPlugin *plugin = plugin_mgr->plugin;
-  MetaPluginClass *klass = META_PLUGIN_GET_CLASS (plugin);
-  MetaDisplay *display = plugin_mgr->compositor->display;
-  gboolean retval = FALSE;
+  MetaPlugin *plugin;
+  MetaPluginClass *klass;
+  MetaDisplay *display;
+  gboolean retval;
+
+  g_return_val_if_fail (plugin_mgr, FALSE);
+
+  plugin = plugin_mgr->plugin;
+  klass = META_PLUGIN_GET_CLASS (plugin);
+  display = plugin_mgr->compositor->display;
+  retval = FALSE;
 
   if (display->display_opening)
     return FALSE;