diff --git a/CHANGES.md b/CHANGES.md
index 9de95b4d15..7543f1c1c7 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -249,6 +249,10 @@ To be released.
     was once called.  [[#965]]
  -  Fixed a bug that `TurnClient` had thrown `InvalidOperationException` when
     reconnecting.  [[#957], [#972]]
+ -  Fixed a bug that `Swarm<T>` had not received block headers after failing
+    to receive previous blocks.  [[#996]]
+ -  Fixed a bug that `Swarm<T>` had thrown `InvalidGenesisBlockException`
+    when reorg its chain repeatedly.  [[#996]]
 
 ### CLI tools
 
@@ -312,6 +316,7 @@ To be released.
 [#980]: https://github.com/planetarium/libplanet/pull/980
 [#981]: https://github.com/planetarium/libplanet/pull/981
 [#991]: https://github.com/planetarium/libplanet/pull/991
+[#996]: https://github.com/planetarium/libplanet/pull/996
 [sleep mode]: https://en.wikipedia.org/wiki/Sleep_mode
 
 
diff --git a/Libplanet/Net/Swarm.cs b/Libplanet/Net/Swarm.cs
index 893ed75a5a..e65ba9efd3 100644
--- a/Libplanet/Net/Swarm.cs
+++ b/Libplanet/Net/Swarm.cs
@@ -1810,10 +1810,7 @@ out HashDigest<SHA256> branchPoint
                     {
                         _logger.Debug("It doesn't need to fork.");
                     }
-
-                    // We can omit this clause if assume every chain shares
-                    // same genesis block...
-                    else if (!BlockChain.ContainsBlock(branchPoint))
+                    else if (!workspace.ContainsBlock(branchPoint))
                     {
                         // FIXME: This behavior can unexpectedly terminate the swarm (and the game
                         // app) if it encounters a peer having a different blockchain, and therefore
@@ -1968,6 +1965,13 @@ await SyncPreviousBlocksAsync(
                         $" {nameof(ProcessFillBlocks)}: {{e}}";
                     _logger.Error(e, msg, e);
                 }
+                finally
+                {
+                    using (await _blockSyncMutex.LockAsync(cancellationToken))
+                    {
+                        _demandBlockHash = null;
+                    }
+                }
             }
         }