diff --git a/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs b/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs
index be47d8e720..404cb601d5 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs
@@ -305,12 +305,9 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
                     var returnBlock = block;
                     block = block.Next;
 
-                    returnBlock.Unpin();
                     returnBlock.Pool?.Return(returnBlock);
                 }
 
-                _tail.Unpin();
-
                 if (_isProducing)
                 {
                     _returnFromOnProducingComplete = _tail;
@@ -381,6 +378,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
 
                 var writeReq = new UvWriteReq(Self._log);
                 writeReq.Init(Self._thread.Loop);
+
                 writeReq.Write(Self._socket, _lockedStart, _lockedEnd, _bufferCount, (_writeReq, status, error, state) =>
                 {
                     _writeReq.Dispose();
@@ -453,6 +451,8 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
                     returnBlock.Unpin();
                     returnBlock.Pool?.Return(returnBlock);
                 }
+
+                _lockedEnd.Block.Unpin();
             }
 
             private void LockWrite()
diff --git a/src/Microsoft.AspNet.Server.Kestrel/Infrastructure/MemoryPoolBlock2.cs b/src/Microsoft.AspNet.Server.Kestrel/Infrastructure/MemoryPoolBlock2.cs
index 2bcd21d9a2..26156c6cc0 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/Infrastructure/MemoryPoolBlock2.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/Infrastructure/MemoryPoolBlock2.cs
@@ -105,15 +105,13 @@ namespace Microsoft.AspNet.Server.Kestrel.Infrastructure
         /// <returns></returns>
         public IntPtr Pin()
         {
+            Debug.Assert(!_pinHandle.IsAllocated);
+
             if (_dataArrayPtr != IntPtr.Zero)
             {
                 // this is a slab managed block - use the native address of the slab which is always locked
                 return _dataArrayPtr;
             }
-            else if (_pinHandle.IsAllocated)
-            {
-                return _pinHandle.AddrOfPinnedObject();
-            }
             else
             {
                 // this is one-time-use memory - lock the managed memory until Unpin is called
diff --git a/src/Microsoft.AspNet.Server.Kestrel/Networking/UvWriteReq.cs b/src/Microsoft.AspNet.Server.Kestrel/Networking/UvWriteReq.cs
index 7330ef3c15..2695036f32 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/Networking/UvWriteReq.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/Networking/UvWriteReq.cs
@@ -85,6 +85,14 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
                 _callback = null;
                 _state = null;
                 Unpin(this);
+
+                var block = start.Block;
+                for (var index = 0; index < nBuffers; index++)
+                {
+                    block.Unpin();
+                    block = block.Next;
+                }
+
                 throw;
             }
         }