1 files changed, 19 insertions, 6 deletions

diff --git a/source/blender/editors/object/object_relations.c b/source/blender/editors/object/object_relations.c
index dbee2e77cf5..ec6c1059ed3 100644
--- a/source/blender/editors/object/object_relations.c
+++ b/source/blender/editors/object/object_relations.c
@@ -1602,7 +1602,7 @@ static void libblock_relink_collection(Collection *collection)
 	}
 }
 
-static void single_object_users_collection(
+static Collection *single_object_users_collection(
         Main *bmain, Scene *scene, Collection *collection,
         const int flag, const bool copy_collections, const bool is_master_collection)
 {
@@ -1623,9 +1623,24 @@ static void single_object_users_collection(
 		}
 	}
 
-	for (CollectionChild *child = collection->children.first; child; child = child->next) {
-		single_object_users_collection(bmain, scene, child->collection, flag, copy_collections, false);
+	/* Since master collection has already be duplicated as part of scene copy, we do not duplictae it here.
+	 * However, this means its children need to be re-added manually here, otherwise their parent lists are empty
+	 * (which will lead to crashes, see T63101). */
+	CollectionChild *child_next, *child = collection->children.first;
+	if (is_master_collection) {
+		BLI_listbase_clear(&collection->children);
+	}
+	for (; child; child = child_next) {
+		child_next = child->next;
+		Collection *collection_child_new = single_object_users_collection(
+		                                       bmain, scene, child->collection, flag, copy_collections, false);
+		if (is_master_collection) {
+			BKE_collection_child_add(bmain, collection, collection_child_new);
+			MEM_freeN(child);
+		}
 	}
+
+	return collection;
 }
 
 /* Warning, sets ID->newid pointers of objects and collections, but does not clear them. */
@@ -1679,9 +1694,7 @@ static void single_object_users(Main *bmain, Scene *scene, View3D *v3d, const in
 	}
 
 	/* Making single user may affect other scenes if they share with current one some collections in their ViewLayer. */
-	for (Scene *sce = bmain->scenes.first; sce != NULL; sce = sce->id.next) {
-		BKE_scene_collection_sync(sce);
-	}
+	BKE_main_collection_sync(bmain);
 }
 
 /* not an especially efficient function, only added so the single user