diff --git a/src/compositor/meta-plugin-manager.c b/src/compositor/meta-plugin-manager.c
index eb684971b..8dfc97a37 100644
--- a/src/compositor/meta-plugin-manager.c
+++ b/src/compositor/meta-plugin-manager.c
@@ -149,7 +149,7 @@ meta_plugin_manager_kill_switch_workspace (MetaPluginManager *plugin_mgr)
 gboolean
 meta_plugin_manager_event_simple (MetaPluginManager *plugin_mgr,
                                   MetaWindowActor   *actor,
-                                  unsigned long      event)
+                                  MetaPluginEffect   event)
 {
   MetaPlugin *plugin = plugin_mgr->plugin;
   MetaPluginClass *klass = META_PLUGIN_GET_CLASS (plugin);
@@ -196,7 +196,7 @@ meta_plugin_manager_event_simple (MetaPluginManager *plugin_mgr,
         }
       break;
     default:
-      g_warning ("Incorrect handler called for event %lu", event);
+      g_warning ("Incorrect handler called for event %d", event);
     }
 
   return retval;
@@ -214,7 +214,7 @@ meta_plugin_manager_event_simple (MetaPluginManager *plugin_mgr,
 gboolean
 meta_plugin_manager_event_maximize (MetaPluginManager *plugin_mgr,
                                     MetaWindowActor   *actor,
-                                    unsigned long      event,
+                                    MetaPluginEffect   event,
                                     gint               target_x,
                                     gint               target_y,
                                     gint               target_width,
@@ -253,7 +253,7 @@ meta_plugin_manager_event_maximize (MetaPluginManager *plugin_mgr,
         }
       break;
     default:
-      g_warning ("Incorrect handler called for event %lu", event);
+      g_warning ("Incorrect handler called for event %d", event);
     }
 
   return retval;
diff --git a/src/compositor/meta-plugin-manager.h b/src/compositor/meta-plugin-manager.h
index 66a22adcd..19773715f 100644
--- a/src/compositor/meta-plugin-manager.h
+++ b/src/compositor/meta-plugin-manager.h
@@ -26,15 +26,15 @@
 #include <meta/screen.h>
 #include <meta/meta-plugin.h>
 
-#define META_PLUGIN_MINIMIZE         (1<<0)
-#define META_PLUGIN_MAXIMIZE         (1<<1)
-#define META_PLUGIN_UNMAXIMIZE       (1<<2)
-#define META_PLUGIN_MAP              (1<<3)
-#define META_PLUGIN_DESTROY          (1<<4)
-#define META_PLUGIN_SWITCH_WORKSPACE (1<<5)
-#define META_PLUGIN_UNMINIMIZE       (1<<6)
-
-#define META_PLUGIN_ALL_EFFECTS      (~0)
+typedef enum {
+  META_PLUGIN_MINIMIZE,
+  META_PLUGIN_MAXIMIZE,
+  META_PLUGIN_UNMAXIMIZE,
+  META_PLUGIN_MAP,
+  META_PLUGIN_DESTROY,
+  META_PLUGIN_SWITCH_WORKSPACE,
+  META_PLUGIN_UNMINIMIZE,
+} MetaPluginEffect;
 
 /**
  * MetaPluginManager: (skip)
@@ -48,11 +48,11 @@ void     meta_plugin_manager_load         (const gchar       *plugin_name);
 
 gboolean meta_plugin_manager_event_simple (MetaPluginManager *mgr,
                                            MetaWindowActor   *actor,
-                                           unsigned long      event);
+                                           MetaPluginEffect   event);
 
 gboolean meta_plugin_manager_event_maximize    (MetaPluginManager *mgr,
                                                 MetaWindowActor   *actor,
-                                                unsigned long      event,
+                                                MetaPluginEffect   event,
                                                 gint               target_x,
                                                 gint               target_y,
                                                 gint               target_width,
diff --git a/src/compositor/meta-window-actor-private.h b/src/compositor/meta-window-actor-private.h
index 5f495d6f1..f014e703e 100644
--- a/src/compositor/meta-window-actor-private.h
+++ b/src/compositor/meta-window-actor-private.h
@@ -8,6 +8,7 @@
 #include <X11/extensions/Xdamage.h>
 #include <meta/compositor-mutter.h>
 #include "meta-surface-actor.h"
+#include "meta-plugin-manager.h"
 
 MetaWindowActor *meta_window_actor_new (MetaWindow *window);
 
@@ -55,8 +56,8 @@ void     meta_window_actor_sync_updates_frozen (MetaWindowActor *self);
 void     meta_window_actor_queue_frame_drawn   (MetaWindowActor *self,
                                                 gboolean         no_delay_frame);
 
-void meta_window_actor_effect_completed (MetaWindowActor *actor,
-                                         gulong           event);
+void meta_window_actor_effect_completed (MetaWindowActor  *actor,
+                                         MetaPluginEffect  event);
 
 MetaSurfaceActor *meta_window_actor_get_surface (MetaWindowActor *self);
 void meta_window_actor_update_surface (MetaWindowActor *self);
diff --git a/src/compositor/meta-window-actor.c b/src/compositor/meta-window-actor.c
index d61c2fb30..a518898e5 100644
--- a/src/compositor/meta-window-actor.c
+++ b/src/compositor/meta-window-actor.c
@@ -1043,7 +1043,7 @@ meta_window_actor_effect_in_progress (MetaWindowActor *self)
 }
 
 static gboolean
-is_freeze_thaw_effect (gulong event)
+is_freeze_thaw_effect (MetaPluginEffect event)
 {
   switch (event)
   {
@@ -1058,8 +1058,8 @@ is_freeze_thaw_effect (gulong event)
 }
 
 static gboolean
-start_simple_effect (MetaWindowActor *self,
-                     gulong        event)
+start_simple_effect (MetaWindowActor  *self,
+                     MetaPluginEffect  event)
 {
   MetaWindowActorPrivate *priv = self->priv;
   MetaCompositor *compositor = priv->compositor;
@@ -1123,8 +1123,8 @@ meta_window_actor_after_effects (MetaWindowActor *self)
 }
 
 void
-meta_window_actor_effect_completed (MetaWindowActor *self,
-                                    gulong           event)
+meta_window_actor_effect_completed (MetaWindowActor  *self,
+                                    MetaPluginEffect  event)
 {
   MetaWindowActorPrivate *priv   = self->priv;
 
@@ -1300,7 +1300,7 @@ meta_window_actor_show (MetaWindowActor   *self,
 {
   MetaWindowActorPrivate *priv = self->priv;
   MetaCompositor *compositor = priv->compositor;
-  gulong event = 0;
+  MetaPluginEffect event;
 
   g_return_if_fail (!priv->visible);
 
@@ -1335,7 +1335,7 @@ meta_window_actor_hide (MetaWindowActor *self,
 {
   MetaWindowActorPrivate *priv = self->priv;
   MetaCompositor *compositor = priv->compositor;
-  gulong event = 0;
+  MetaPluginEffect event = 0;
 
   g_return_if_fail (priv->visible);