diff --git a/criu/cr-dump.c b/criu/cr-dump.c
index 249c02226..1c1962e8f 100644
--- a/criu/cr-dump.c
+++ b/criu/cr-dump.c
@@ -811,6 +811,7 @@ static int dump_task_core_all(struct parasite_ctl *ctl, struct pstree_item *item
 			goto err;
 	}
 
+	core->thread_core->has_cg_set = true;
 	cg_set = &core->thread_core->cg_set;
 	ret = dump_thread_cgroup(item, cg_set, info, -1);
 	if (ret)
@@ -1436,6 +1437,7 @@ static int dump_task_cgroup(struct parasite_ctl *parasite_ctl, const struct pstr
 				return -1;
 		}
 
+		core->thread_core->has_cg_set = true;
 		if (dump_thread_cgroup(item, &core->thread_core->cg_set, info, i))
 			return -1;
 	}
diff --git a/criu/cr-restore.c b/criu/cr-restore.c
index 195fa5639..f02e95f6d 100644
--- a/criu/cr-restore.c
+++ b/criu/cr-restore.c
@@ -1354,10 +1354,14 @@ static inline int fork_with_pid(struct pstree_item *item)
 		 * Zombie tasks' cgroup is not dumped/restored.
 		 * cg_set == 0 is skipped in prepare_task_cgroup()
 		 */
-		if (item->pid->state == TASK_DEAD)
+		if (item->pid->state == TASK_DEAD) {
 			rsti(item)->cg_set = 0;
-		else
-			rsti(item)->cg_set = ca.core->thread_core->cg_set;
+		} else {
+			if (ca.core->thread_core->has_cg_set)
+				rsti(item)->cg_set = ca.core->thread_core->cg_set;
+			else
+				rsti(item)->cg_set = ca.core->tc->cg_set;
+		}
 
 		if (ca.core->tc->has_stop_signo)
 			item->pid->stop_signo = ca.core->tc->stop_signo;
@@ -3824,7 +3828,7 @@ static int sigreturn_restore(pid_t pid, struct task_restore_args *task_args, uns
 		thread_args[i].clear_tid_addr = CORE_THREAD_ARCH_INFO(tcore)->clear_tid_addr;
 		core_get_tls(tcore, &thread_args[i].tls);
 
-		if (rsti(current)->cg_set != tcore->thread_core->cg_set) {
+		if (tcore->thread_core->has_cg_set && rsti(current)->cg_set != tcore->thread_core->cg_set) {
 			thread_args[i].cg_set = tcore->thread_core->cg_set;
 			thread_args[i].cgroupd_sk = dup(get_service_fd(CGROUPD_SK));
 		} else {
diff --git a/images/core.proto b/images/core.proto
index bc8b7a488..eddd1dc55 100644
--- a/images/core.proto
+++ b/images/core.proto
@@ -106,7 +106,7 @@ message thread_core_entry {
 	optional string			comm		= 13;
 	optional uint64			blk_sigset_extended	= 14;
 	optional rseq_entry		rseq_entry	= 15;
-	required uint32			cg_set		= 16;
+	optional uint32			cg_set		= 16;
 }
 
 message task_rlimits_entry {