diff --git a/src/core/meta-idle-monitor-native.c b/src/core/meta-idle-monitor-native.c
index eb3ab6a26..a2c5c3a61 100644
--- a/src/core/meta-idle-monitor-native.c
+++ b/src/core/meta-idle-monitor-native.c
@@ -40,6 +40,12 @@ struct _MetaIdleMonitorNativeClass
   MetaIdleMonitorClass parent_class;
 };
 
+typedef struct {
+  MetaIdleMonitorWatch base;
+
+  GSource *timeout_source;
+} MetaIdleMonitorWatchNative;
+
 G_DEFINE_TYPE (MetaIdleMonitorNative, meta_idle_monitor_native, META_TYPE_IDLE_MONITOR)
 
 static gint64
@@ -61,10 +67,11 @@ native_dispatch_timeout (GSource     *source,
                          GSourceFunc  callback,
                          gpointer     user_data)
 {
-  MetaIdleMonitorWatch *watch = user_data;
+  MetaIdleMonitorWatchNative *watch_native = user_data;
+  MetaIdleMonitorWatch *watch = (MetaIdleMonitorWatch *) watch;
 
   _meta_idle_monitor_watch_fire (watch);
-  g_source_set_ready_time (watch->timeout_source, -1);
+  g_source_set_ready_time (watch_native->timeout_source, -1);
   return TRUE;
 }
 
@@ -75,6 +82,31 @@ static GSourceFuncs native_source_funcs = {
   NULL, /* finalize */
 };
 
+static void
+free_watch (gpointer data)
+{
+  MetaIdleMonitorWatchNative *watch_native = data;
+  MetaIdleMonitorWatch *watch = (MetaIdleMonitorWatch *) watch_native;
+  MetaIdleMonitor *monitor = watch->monitor;
+
+  g_object_ref (monitor);
+
+  if (watch->idle_source_id)
+    {
+      g_source_remove (watch->idle_source_id);
+      watch->idle_source_id = 0;
+    }
+
+  if (watch->notify != NULL)
+    watch->notify (watch->user_data);
+
+  if (watch_native->timeout_source != NULL)
+    g_source_destroy (watch_native->timeout_source);
+
+  g_object_unref (monitor);
+  g_slice_free (MetaIdleMonitorWatchNative, watch_native);
+}
+
 static MetaIdleMonitorWatch *
 meta_idle_monitor_native_make_watch (MetaIdleMonitor           *monitor,
                                     guint64                    timeout_msec,
@@ -82,8 +114,12 @@ meta_idle_monitor_native_make_watch (MetaIdleMonitor           *monitor,
                                     gpointer                   user_data,
                                     GDestroyNotify             notify)
 {
+  MetaIdleMonitorWatchNative *watch_native;
   MetaIdleMonitorWatch *watch;
 
+  watch_native = g_slice_new0 (MetaIdleMonitorWatchNative);
+  watch = (MetaIdleMonitorWatch *) watch_native;
+
   watch = g_slice_new0 (MetaIdleMonitorWatch);
   watch->monitor = monitor;
   watch->id = get_next_watch_serial ();
@@ -101,7 +137,7 @@ meta_idle_monitor_native_make_watch (MetaIdleMonitor           *monitor,
       g_source_attach (source, NULL);
       g_source_unref (source);
 
-      watch->timeout_source = source;
+      watch_native->timeout_source = source;
     }
 
   return watch;
@@ -117,8 +153,11 @@ meta_idle_monitor_native_class_init (MetaIdleMonitorNativeClass *klass)
 }
 
 static void
-meta_idle_monitor_native_init (MetaIdleMonitorNative *monitor)
+meta_idle_monitor_native_init (MetaIdleMonitorNative *monitor_native)
 {
+  MetaIdleMonitor *monitor = META_IDLE_MONITOR (monitor_native);
+
+  monitor->watches = g_hash_table_new_full (NULL, NULL, NULL, free_watch);
 }
 
 typedef struct {
@@ -131,7 +170,8 @@ check_native_watch (gpointer key,
                     gpointer value,
                     gpointer user_data)
 {
-  MetaIdleMonitorWatch *watch = value;
+  MetaIdleMonitorWatchNative *watch_native = value;
+  MetaIdleMonitorWatch *watch = (MetaIdleMonitorWatch *) watch_native;
   CheckNativeClosure *closure = user_data;
   gboolean steal;
 
@@ -142,7 +182,7 @@ check_native_watch (gpointer key,
     }
   else
     {
-      g_source_set_ready_time (watch->timeout_source,
+      g_source_set_ready_time (watch_native->timeout_source,
                                closure->monitor->last_event_time +
                                watch->timeout_msec * 1000);
       steal = FALSE;
diff --git a/src/core/meta-idle-monitor-private.h b/src/core/meta-idle-monitor-private.h
index b34ca83d1..f3fc4c732 100644
--- a/src/core/meta-idle-monitor-private.h
+++ b/src/core/meta-idle-monitor-private.h
@@ -37,13 +37,7 @@ typedef struct
   gpointer		    user_data;
   GDestroyNotify            notify;
   guint64                   timeout_msec;
-
-  /* x11 */
-  XSyncAlarm                xalarm;
   int                       idle_source_id;
-
-  /* wayland */
-  GSource                  *timeout_source;
 } MetaIdleMonitorWatch;
 
 struct _MetaIdleMonitor
diff --git a/src/core/meta-idle-monitor-xsync.c b/src/core/meta-idle-monitor-xsync.c
index b1f47ba18..8d3fcc73c 100644
--- a/src/core/meta-idle-monitor-xsync.c
+++ b/src/core/meta-idle-monitor-xsync.c
@@ -40,6 +40,12 @@ struct _MetaIdleMonitorXSyncClass
   MetaIdleMonitorClass parent_class;
 };
 
+typedef struct {
+  MetaIdleMonitorWatch base;
+
+  XSyncAlarm xalarm;
+} MetaIdleMonitorWatchXSync;
+
 G_DEFINE_TYPE (MetaIdleMonitorXSync, meta_idle_monitor_xsync, META_TYPE_IDLE_MONITOR)
 
 static gint64
@@ -101,10 +107,11 @@ static void
 check_x11_watch (gpointer data,
                  gpointer user_data)
 {
-  MetaIdleMonitorWatch *watch = data;
+  MetaIdleMonitorWatchXSync *watch_xsync = data;
+  MetaIdleMonitorWatch *watch = (MetaIdleMonitorWatch *) watch_xsync;
   XSyncAlarm alarm = (XSyncAlarm) user_data;
 
-  if (watch->xalarm != alarm)
+  if (watch_xsync->xalarm != alarm)
     return;
 
   _meta_idle_monitor_watch_fire (watch);
@@ -215,6 +222,35 @@ get_next_watch_serial (void)
   return serial;
 }
 
+static void
+free_watch (gpointer data)
+{
+  MetaIdleMonitorWatchXSync *watch_xsync = data;
+  MetaIdleMonitorWatch *watch = (MetaIdleMonitorWatch *) watch_xsync;
+  MetaIdleMonitor *monitor = watch->monitor;
+
+  g_object_ref (monitor);
+
+  if (watch->idle_source_id)
+    {
+      g_source_remove (watch->idle_source_id);
+      watch->idle_source_id = 0;
+    }
+
+  if (watch->notify != NULL)
+    watch->notify (watch->user_data);
+
+  if (watch_xsync->xalarm != monitor->user_active_alarm &&
+      watch_xsync->xalarm != None)
+    {
+      XSyncDestroyAlarm (monitor->display, watch_xsync->xalarm);
+      g_hash_table_remove (monitor->alarms, (gpointer) watch_xsync->xalarm);
+    }
+
+  g_object_unref (monitor);
+  g_slice_free (MetaIdleMonitorWatchXSync, watch_xsync);
+}
+
 static MetaIdleMonitorWatch *
 meta_idle_monitor_xsync_make_watch (MetaIdleMonitor           *monitor,
                                     guint64                    timeout_msec,
@@ -222,9 +258,12 @@ meta_idle_monitor_xsync_make_watch (MetaIdleMonitor           *monitor,
                                     gpointer                   user_data,
                                     GDestroyNotify             notify)
 {
+  MetaIdleMonitorWatchXSync *watch_xsync;
   MetaIdleMonitorWatch *watch;
 
-  watch = g_slice_new0 (MetaIdleMonitorWatch);
+  watch_xsync = g_slice_new0 (MetaIdleMonitorWatchXSync);
+  watch = (MetaIdleMonitorWatch *) watch_xsync;
+
   watch->monitor = monitor;
   watch->id = get_next_watch_serial ();
   watch->callback = callback;
@@ -236,16 +275,16 @@ meta_idle_monitor_xsync_make_watch (MetaIdleMonitor           *monitor,
     {
       if (timeout_msec != 0)
         {
-          watch->xalarm = _xsync_alarm_set (monitor, XSyncPositiveTransition, timeout_msec, TRUE);
+          watch_xsync->xalarm = _xsync_alarm_set (monitor, XSyncPositiveTransition, timeout_msec, TRUE);
 
-          g_hash_table_add (monitor->alarms, (gpointer) watch->xalarm);
+          g_hash_table_add (monitor->alarms, (gpointer) watch_xsync->xalarm);
 
           if (meta_idle_monitor_get_idletime (monitor) > (gint64)timeout_msec)
             watch->idle_source_id = g_idle_add (fire_watch_idle, watch);
         }
       else
         {
-          watch->xalarm = monitor->user_active_alarm;
+          watch_xsync->xalarm = monitor->user_active_alarm;
 
           set_alarm_enabled (monitor->display, monitor->user_active_alarm, TRUE);
         }
@@ -268,8 +307,11 @@ meta_idle_monitor_xsync_class_init (MetaIdleMonitorXSyncClass *klass)
 }
 
 static void
-meta_idle_monitor_xsync_init (MetaIdleMonitorXSync *monitor)
+meta_idle_monitor_xsync_init (MetaIdleMonitorXSync *monitor_xsync)
 {
+  MetaIdleMonitor *monitor = META_IDLE_MONITOR (monitor_xsync);
+
+  monitor->watches = g_hash_table_new_full (NULL, NULL, NULL, free_watch);
 }
 
 void
diff --git a/src/core/meta-idle-monitor.c b/src/core/meta-idle-monitor.c
index 522727004..4230679cc 100644
--- a/src/core/meta-idle-monitor.c
+++ b/src/core/meta-idle-monitor.c
@@ -85,40 +85,6 @@ _meta_idle_monitor_watch_fire (MetaIdleMonitorWatch *watch)
   g_object_unref (monitor);
 }
 
-static void
-idle_monitor_watch_free (MetaIdleMonitorWatch *watch)
-{
-  MetaIdleMonitor *monitor;
-
-  if (watch == NULL)
-    return;
-
-  monitor = watch->monitor;
-  g_object_ref (monitor);
-
-  if (watch->idle_source_id)
-    {
-      g_source_remove (watch->idle_source_id);
-      watch->idle_source_id = 0;
-    }
-
-  if (watch->notify != NULL)
-    watch->notify (watch->user_data);
-
-  if (watch->xalarm != monitor->user_active_alarm &&
-      watch->xalarm != None)
-    {
-      XSyncDestroyAlarm (monitor->display, watch->xalarm);
-      g_hash_table_remove (monitor->alarms, (gpointer) watch->xalarm);
-    }
-
-  if (watch->timeout_source != NULL)
-    g_source_destroy (watch->timeout_source);
-
-  g_object_unref (monitor);
-  g_slice_free (MetaIdleMonitorWatch, watch);
-}
-
 static void
 meta_idle_monitor_dispose (GObject *object)
 {
@@ -193,11 +159,6 @@ meta_idle_monitor_class_init (MetaIdleMonitorClass *klass)
 static void
 meta_idle_monitor_init (MetaIdleMonitor *monitor)
 {
-  monitor->watches = g_hash_table_new_full (NULL,
-                                                  NULL,
-                                                  NULL,
-                                                  (GDestroyNotify)idle_monitor_watch_free);
-
   monitor->alarms = g_hash_table_new (NULL, NULL);
 }