--- a/src/lib-storage/mailbox-list-private.h	Mon Jun 26 20:10:17 2017 +0300
+++ b/src/lib-storage/mailbox-list-private.h	Mon Jun 26 18:19:17 2017 +0300
@@ -220,6 +220,9 @@
 					 const struct dirent *d);
 bool mailbox_list_try_get_absolute_path(struct mailbox_list *list,
 					const char **name);
+void mailbox_permissions_copy(struct mailbox_permissions *dest,
+			      const struct mailbox_permissions *src,
+			      pool_t pool);
 
 void mailbox_list_add_change(struct mailbox_list *list,
 			     enum mailbox_log_record_type type,

--- a/src/lib-storage/mailbox-list.c	Mon Jun 26 20:10:17 2017 +0300
+++ b/src/lib-storage/mailbox-list.c	Mon Jun 26 18:19:17 2017 +0300
@@ -1025,6 +1025,15 @@
 	}
 }
 
+void mailbox_permissions_copy(struct mailbox_permissions *dest,
+			      const struct mailbox_permissions *src,
+			      pool_t pool)
+{
+	*dest = *src;
+	dest->file_create_gid_origin =
+		p_strdup(pool, src->file_create_gid_origin);
+}
+
 static const char *
 get_expanded_path(const char *unexpanded_start, const char *unexpanded_stop,
 		  const char *expanded_full)