2 files changed, 18 insertions, 1 deletions
diff --git a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc
index 108f5f04879..e141925725b 100644
--- a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc
+++ b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc
@@ -32,7 +32,8 @@
 namespace DEG {
 
 RuntimeBackup::RuntimeBackup(const Depsgraph *depsgraph)
-    : animation_backup(depsgraph),
+    : have_backup(nullptr),
+      animation_backup(depsgraph),
       scene_backup(depsgraph),
       sound_backup(depsgraph),
       object_backup(depsgraph),
@@ -48,6 +49,7 @@ void RuntimeBackup::init_from_id(ID *id)
   if (!deg_copy_on_write_is_expanded(id)) {
     return;
   }
+  have_backup = true;
 
   animation_backup.init_from_id(id);
 
@@ -83,6 +85,10 @@ void RuntimeBackup::init_from_id(ID *id)
 
 void RuntimeBackup::restore_to_id(ID *id)
 {
+  if (!have_backup) {
+    return;
+  }
+
   animation_backup.restore_to_id(id);
 
   const ID_Type id_type = GS(id->name);
diff --git a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h
index c818c1f7064..d1a30652b36 100644
--- a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h
+++ b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h
@@ -46,6 +46,17 @@ class RuntimeBackup {
   /* Restore fields to the given ID. */
   void restore_to_id(ID *id);
 
+  /* Denotes whether init_from_id did put anything into the backup storage.
+   * This will not be the case when init_from_id() is called for an ID which has never been
+   * copied-on-write. In this case there is no need to backup or restore anything.
+   *
+   * It also allows to have restore() logic to be symmetrical to init() without need to worry
+   * that init() might not have happenned.
+   *
+   * In practice this is used by audio system to lock audio while scene is going through
+   * copy-on-write mechanism. */
+  bool have_backup;
+
   AnimationBackup animation_backup;
   SceneBackup scene_backup;
   SoundBackup sound_backup;