diff --git a/dbms/include/DB/Storages/MergeTree/ReplicatedMergeTreeBlockOutputStream.h b/dbms/include/DB/Storages/MergeTree/ReplicatedMergeTreeBlockOutputStream.h
index 2d4ee2a153f..ea8f4b7dbc7 100644
--- a/dbms/include/DB/Storages/MergeTree/ReplicatedMergeTreeBlockOutputStream.h
+++ b/dbms/include/DB/Storages/MergeTree/ReplicatedMergeTreeBlockOutputStream.h
@@ -17,12 +17,12 @@ public:
 
 	void write(const Block & block) override
 	{
+		assertSessionIsNotExpired();
 		auto part_blocks = storage.writer.splitBlockIntoParts(block);
 
 		for (auto & current_block : part_blocks)
 		{
-			if (storage.zookeeper->expired())
-				throw Exception("ZooKeeper session has been expired.", ErrorCodes::NO_ZOOKEEPER);
+			assertSessionIsNotExpired();
 
 			/// TODO Можно ли здесь не блокировать структуру таблицы?
 			storage.data.delayInsertIfNeeded(&storage.restarting_event);
@@ -145,6 +145,14 @@ private:
 	size_t block_index;
 
 	Logger * log;
+
+
+	/// Позволяет проверить, что сессия в ZooKeeper ещё жива.
+	void assertSessionIsNotExpired()
+	{
+		if (storage.zookeeper->expired())
+			throw Exception("ZooKeeper session has been expired.", ErrorCodes::NO_ZOOKEEPER);
+	}
 };
 
 }
diff --git a/dbms/src/Storages/StorageReplicatedMergeTree.cpp b/dbms/src/Storages/StorageReplicatedMergeTree.cpp
index ec9d0410297..6c6efb0642d 100644
--- a/dbms/src/Storages/StorageReplicatedMergeTree.cpp
+++ b/dbms/src/Storages/StorageReplicatedMergeTree.cpp
@@ -2026,16 +2026,9 @@ void StorageReplicatedMergeTree::restartingThread()
 			{
 				LOG_WARNING(log, "ZooKeeper session has expired. Switching to a new session.");
 
-				{
-					/// Запретим писать в таблицу, пока подменяем zookeeper.
-					auto structure_lock = lockDataForAlter();
-
-					partialShutdown();
-
-					zookeeper = context.getZooKeeper();
-
-					is_read_only = true;
-				}
+				partialShutdown();
+				zookeeper = context.getZooKeeper();
+				is_read_only = true;
 
 				while (!permanent_shutdown_called && !tryStartup())
 					restarting_event.tryWait(10 * 1000);
@@ -2043,11 +2036,7 @@ void StorageReplicatedMergeTree::restartingThread()
 				if (permanent_shutdown_called)
 					break;
 
-				{
-					auto structure_lock = lockDataForAlter();
-
-					is_read_only = false;
-				}
+				is_read_only = false;
 			}
 
 			restarting_event.tryWait(60 * 1000);