diff --git a/src/backends/native/meta-kms-update-private.h b/src/backends/native/meta-kms-update-private.h
index bf3326ac4..32bb68bb8 100644
--- a/src/backends/native/meta-kms-update-private.h
+++ b/src/backends/native/meta-kms-update-private.h
@@ -34,6 +34,7 @@ typedef struct _MetaKmsProperty
 
 typedef struct _MetaKmsPlaneAssignment
 {
+  MetaKmsUpdate *update;
   MetaKmsCrtc *crtc;
   MetaKmsPlane *plane;
   uint32_t fb_id;
@@ -67,6 +68,10 @@ typedef struct _MetaKmsPageFlip
   gpointer custom_page_flip_user_data;
 } MetaKmsPageFlip;
 
+void meta_kms_update_seal (MetaKmsUpdate *update);
+
+gboolean meta_kms_update_is_sealed (MetaKmsUpdate *update);
+
 void meta_kms_update_set_connector_property (MetaKmsUpdate    *update,
                                              MetaKmsConnector *connector,
                                              uint32_t          prop_id,
diff --git a/src/backends/native/meta-kms-update.c b/src/backends/native/meta-kms-update.c
index 439e917ba..95b2464b6 100644
--- a/src/backends/native/meta-kms-update.c
+++ b/src/backends/native/meta-kms-update.c
@@ -27,6 +27,8 @@
 
 struct _MetaKmsUpdate
 {
+  gboolean is_sealed;
+
   MetaPowerSave power_save;
   GList *mode_sets;
   GList *plane_assignments;
@@ -81,8 +83,11 @@ meta_kms_update_assign_plane (MetaKmsUpdate        *update,
 {
   MetaKmsPlaneAssignment *plane_assignment;
 
+  g_assert (!meta_kms_update_is_sealed (update));
+
   plane_assignment = g_new0 (MetaKmsPlaneAssignment, 1);
   *plane_assignment = (MetaKmsPlaneAssignment) {
+    .update = update,
     .crtc = crtc,
     .plane = plane,
     .fb_id = fb_id,
@@ -104,6 +109,8 @@ meta_kms_update_mode_set (MetaKmsUpdate   *update,
 {
   MetaKmsModeSet *mode_set;
 
+  g_assert (!meta_kms_update_is_sealed (update));
+
   mode_set = g_new0 (MetaKmsModeSet, 1);
   *mode_set = (MetaKmsModeSet) {
     .crtc = crtc,
@@ -122,6 +129,8 @@ meta_kms_update_set_connector_property (MetaKmsUpdate    *update,
 {
   MetaKmsConnectorProperty *prop;
 
+  g_assert (!meta_kms_update_is_sealed (update));
+
   prop = g_new0 (MetaKmsConnectorProperty, 1);
   *prop = (MetaKmsConnectorProperty) {
     .connector = connector,
@@ -141,6 +150,8 @@ meta_kms_update_page_flip (MetaKmsUpdate                 *update,
 {
   MetaKmsPageFlip *page_flip;
 
+  g_assert (!meta_kms_update_is_sealed (update));
+
   page_flip = g_new0 (MetaKmsPageFlip, 1);
   *page_flip = (MetaKmsPageFlip) {
     .crtc = crtc,
@@ -161,6 +172,8 @@ meta_kms_update_custom_page_flip (MetaKmsUpdate                 *update,
 {
   MetaKmsPageFlip *page_flip;
 
+  g_assert (!meta_kms_update_is_sealed (update));
+
   page_flip = g_new0 (MetaKmsPageFlip, 1);
   *page_flip = (MetaKmsPageFlip) {
     .crtc = crtc,
@@ -180,6 +193,8 @@ meta_kms_plane_assignment_set_plane_property (MetaKmsPlaneAssignment *plane_assi
 {
   MetaKmsProperty *plane_prop;
 
+  g_assert (!meta_kms_update_is_sealed (plane_assignment->update));
+
   plane_prop = meta_kms_property_new (prop_id, value);
 
   plane_assignment->plane_properties =
@@ -216,6 +231,18 @@ meta_kms_update_has_mode_set (MetaKmsUpdate *update)
   return !!update->mode_sets;
 }
 
+void
+meta_kms_update_seal (MetaKmsUpdate *update)
+{
+  update->is_sealed = TRUE;
+}
+
+gboolean
+meta_kms_update_is_sealed (MetaKmsUpdate *update)
+{
+  return update->is_sealed;
+}
+
 MetaKmsUpdate *
 meta_kms_update_new (void)
 {
diff --git a/src/backends/native/meta-kms.c b/src/backends/native/meta-kms.c
index 976eae230..641aaa198 100644
--- a/src/backends/native/meta-kms.c
+++ b/src/backends/native/meta-kms.c
@@ -202,6 +202,8 @@ meta_kms_post_update_sync (MetaKms        *kms,
                            MetaKmsUpdate  *update,
                            GError        **error)
 {
+  meta_kms_update_seal (update);
+
   return meta_kms_run_impl_task_sync (kms,
                                       meta_kms_update_process_in_impl,
                                       update,