diff --git a/Libplanet.Tests/Menees.Analyzers.Settings.xml b/Libplanet.Tests/Menees.Analyzers.Settings.xml
index 592faa78276..8af8c63e109 100644
--- a/Libplanet.Tests/Menees.Analyzers.Settings.xml
+++ b/Libplanet.Tests/Menees.Analyzers.Settings.xml
@@ -2,5 +2,5 @@
 <Menees.Analyzers.Settings>
   <MaxLineColumns>100</MaxLineColumns>
   <MaxMethodLines>300</MaxMethodLines>
-  <MaxFileLines>2550</MaxFileLines>
+  <MaxFileLines>2600</MaxFileLines>
 </Menees.Analyzers.Settings>
diff --git a/Libplanet.Tests/Net/SwarmTest.cs b/Libplanet.Tests/Net/SwarmTest.cs
index a4231f0abda..17959b1cf15 100644
--- a/Libplanet.Tests/Net/SwarmTest.cs
+++ b/Libplanet.Tests/Net/SwarmTest.cs
@@ -2430,6 +2430,35 @@ public async Task BlockDemand()
             }
         }
 
+        [Fact]
+        public async Task ResetBlockDemandIfNotChanged()
+        {
+            var minerKey = new PrivateKey();
+            Swarm<DumbAction> sender = CreateSwarm();
+            Swarm<DumbAction> receiver = CreateSwarm();
+            for (var i = 0; i < 20; i++)
+            {
+                await sender.BlockChain.MineBlock(minerKey.ToAddress());
+            }
+
+            Block<DumbAction> lowerBlock = sender.BlockChain[19],
+                higherBlock = sender.BlockChain[20];
+
+            await StartAsync(sender);
+            await StartAsync(receiver);
+            await BootstrapAsync(sender, receiver.AsPeer);
+
+            sender.BroadcastBlock(lowerBlock);
+            await receiver.FillBlocksAsyncStarted.WaitAsync();
+            sender.BroadcastBlock(higherBlock);
+            await receiver.ProcessFillBlocksFinished.WaitAsync();
+
+            Assert.NotNull(receiver.BlockDemand);
+            Assert.Equal(
+                higherBlock.Hash,
+                new HashDigest<SHA256>(receiver.BlockDemand.Value.Header.Hash));
+        }
+
         private async Task<Task> StartAsync<T>(
             Swarm<T> swarm,
             CancellationToken cancellationToken = default
diff --git a/Libplanet/Net/Swarm.cs b/Libplanet/Net/Swarm.cs
index e798cf19925..30b2a87efe5 100644
--- a/Libplanet/Net/Swarm.cs
+++ b/Libplanet/Net/Swarm.cs
@@ -233,6 +233,8 @@ static Swarm()
 
         internal AsyncAutoResetEvent FillBlocksAsyncFailed { get; } = new AsyncAutoResetEvent();
 
+        internal AsyncAutoResetEvent ProcessFillBlocksFinished { get; } = new AsyncAutoResetEvent();
+
         internal SwarmOptions Options { get; }
 
         /// <summary>
@@ -1716,8 +1718,9 @@ CancellationToken cancellationToken
                     continue;
                 }
 
-                BoundPeer peer = BlockDemand.Value.Peer;
-                var hash = new HashDigest<SHA256>(BlockDemand.Value.Header.Hash.ToArray());
+                BlockDemand blockDemand = BlockDemand.Value;
+                BoundPeer peer = blockDemand.Peer;
+                var hash = new HashDigest<SHA256>(blockDemand.Header.Hash.ToArray());
 
                 try
                 {
@@ -1757,11 +1760,14 @@ CancellationToken cancellationToken
                 {
                     using (await _blockSyncMutex.LockAsync(cancellationToken))
                     {
-                        // FIXME: Should only reset when BlockDemand has not changed
-                        // from the beginning of this operation.
-                        _logger.Debug($"{nameof(ProcessFillBlocks)}() finished. " +
-                                      $"Reset {nameof(BlockDemand)}...");
-                        BlockDemand = null;
+                        _logger.Debug($"{nameof(ProcessFillBlocks)}() finished.");
+                        if (BlockDemand.Equals(blockDemand))
+                        {
+                            _logger.Debug($"Reset {nameof(BlockDemand)}...");
+                            BlockDemand = null;
+                        }
+
+                        ProcessFillBlocksFinished.Set();
                     }
                 }
             }