diff --git a/Enyim.Caching/MemcachedClient.cs b/Enyim.Caching/MemcachedClient.cs
index 31d2c3f0..a9bf0f4e 100755
--- a/Enyim.Caching/MemcachedClient.cs
+++ b/Enyim.Caching/MemcachedClient.cs
@@ -619,7 +619,7 @@ protected virtual bool PerformConcatenate(ConcatenationMode mode, string key, re
 
 			if (node != null)
 			{
-				var command = this.pool.OperationFactory.Concat(mode, hashedKey, 0, data);
+				var command = this.pool.OperationFactory.Concat(mode, hashedKey, cas, data);
 				var retval = node.Execute(command);
 
 				cas = command.CasValue;
diff --git a/Membase/MembaseClient.cs b/Membase/MembaseClient.cs
index 8031a423..687659d8 100644
--- a/Membase/MembaseClient.cs
+++ b/Membase/MembaseClient.cs
@@ -143,7 +143,7 @@ protected override bool PerformConcatenate(ConcatenationMode mode, string key, r
 
 			if (node != null)
 			{
-				var command = this.Pool.OperationFactory.Concat(mode, hashedKey, 0, data);
+				var command = this.Pool.OperationFactory.Concat(mode, hashedKey, cas, data);
 				var retval = this.ExecuteWithRedirect(node, command);
 
 				cas = command.CasValue;
diff --git a/MemcachedTest/BinaryMemcachedClientTest.cs b/MemcachedTest/BinaryMemcachedClientTest.cs
index 31fd88b3..552ff704 100644
--- a/MemcachedTest/BinaryMemcachedClientTest.cs
+++ b/MemcachedTest/BinaryMemcachedClientTest.cs
@@ -84,6 +84,58 @@ public virtual void CASTest()
 				Assert.AreEqual(r5.Result, "baz", "Invalid data returned; excpected 'baz'.");
 			}
 		}
+
+		[TestCase]
+		public void AppendCASTest()
+		{
+			using (MemcachedClient client = GetClient())
+			{
+				// store the item
+				var r1 = client.Cas(StoreMode.Set, "CasAppend", "foo");
+
+				Assert.IsTrue(r1.Result, "Initial set failed.");
+				Assert.AreNotEqual(r1.Cas, 0, "No cas value was returned.");
+
+				var r2 = client.Append("CasAppend", r1.Cas, new System.ArraySegment<byte>(new byte[] { (byte)'l' }));
+
+				Assert.IsTrue(r2.Result, "Append should have succeeded.");
+
+				// get back the item and check the cas value (it should match the cas from the set)
+				var r3 = client.GetWithCas<string>("CasAppend");
+
+				Assert.AreEqual(r3.Result, "fool", "Invalid data returned; expected 'fool'.");
+				Assert.AreEqual(r2.Cas, r3.Cas, "Cas values r2:r3 do not match.");
+
+				var r4 = client.Append("CasAppend", r1.Cas, new System.ArraySegment<byte>(new byte[] { (byte)'l' }));
+				Assert.IsFalse(r4.Result, "Append with invalid CAS should have failed.");
+			}
+		}
+
+		[TestCase]
+		public void PrependCASTest()
+		{
+			using (MemcachedClient client = GetClient())
+			{
+				// store the item
+				var r1 = client.Cas(StoreMode.Set, "CasPrepend", "ool");
+
+				Assert.IsTrue(r1.Result, "Initial set failed.");
+				Assert.AreNotEqual(r1.Cas, 0, "No cas value was returned.");
+
+				var r2 = client.Prepend("CasPrepend", r1.Cas, new System.ArraySegment<byte>(new byte[] { (byte)'f' }));
+
+				Assert.IsTrue(r2.Result, "Prepend should have succeeded.");
+
+				// get back the item and check the cas value (it should match the cas from the set)
+				var r3 = client.GetWithCas<string>("CasPrepend");
+
+				Assert.AreEqual(r3.Result, "fool", "Invalid data returned; expected 'fool'.");
+				Assert.AreEqual(r2.Cas, r3.Cas, "Cas values r2:r3 do not match.");
+
+				var r4 = client.Prepend("CasPrepend", r1.Cas, new System.ArraySegment<byte>(new byte[] { (byte)'l' }));
+				Assert.IsFalse(r4.Result, "Prepend with invalid CAS should have failed.");
+			}
+		}
 	}
 }