diff --git a/Microsoft.Azure.Cosmos/src/Headers/Headers.cs b/Microsoft.Azure.Cosmos/src/Headers/Headers.cs
index d469eed820..8cc4f9fa60 100644
--- a/Microsoft.Azure.Cosmos/src/Headers/Headers.cs
+++ b/Microsoft.Azure.Cosmos/src/Headers/Headers.cs
@@ -425,7 +425,7 @@ internal Headers Clone()
             Headers clone = new Headers();
             foreach (string key in this.CosmosMessageHeaders.AllKeys())
             {
-                clone.Add(key, this.CosmosMessageHeaders.Get(key));
+                clone.CosmosMessageHeaders[key] = this.CosmosMessageHeaders.Get(key);
             }
 
             return clone;
diff --git a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/HeadersTests.cs b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/HeadersTests.cs
index f451241d39..2f58b6e5c7 100644
--- a/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/HeadersTests.cs
+++ b/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/HeadersTests.cs
@@ -171,5 +171,86 @@ public void TestAllKeysWithKnownProperties()
             Assert.IsTrue(allKeys.Contains(HttpConstants.HttpHeaders.Continuation));
             Assert.IsTrue(allKeys.Contains(WFConstants.BackendHeaders.SubStatus));
         }
+
+        [TestMethod]
+        public void TestHeadersClone()
+        {
+            Headers Headers = new Headers();
+            Headers.CosmosMessageHeaders[Key] = Guid.NewGuid().ToString();
+            Headers.ContinuationToken = Guid.NewGuid().ToString();
+            Headers.CosmosMessageHeaders[HttpConstants.HttpHeaders.RetryAfterInMilliseconds] = "20";
+            Headers.Add(WFConstants.BackendHeaders.SubStatus, "1002");
+            Headers.PartitionKey = Guid.NewGuid().ToString();
+            string[] allKeys = Headers.AllKeys();
+            Assert.IsTrue(allKeys.Contains(Key));
+            Assert.IsTrue(allKeys.Contains(HttpConstants.HttpHeaders.PartitionKey));
+            Assert.IsTrue(allKeys.Contains(HttpConstants.HttpHeaders.RetryAfterInMilliseconds));
+            Assert.IsTrue(allKeys.Contains(HttpConstants.HttpHeaders.Continuation));
+            Assert.IsTrue(allKeys.Contains(WFConstants.BackendHeaders.SubStatus));
+
+            Headers clone = Headers.Clone();
+            Assert.IsNotNull(clone);
+            string[] keys = clone.AllKeys();
+            Assert.IsTrue(keys.Contains(Key));
+            Assert.IsTrue(keys.Contains(HttpConstants.HttpHeaders.PartitionKey));
+            Assert.IsTrue(keys.Contains(HttpConstants.HttpHeaders.RetryAfterInMilliseconds));
+            Assert.IsTrue(keys.Contains(HttpConstants.HttpHeaders.Continuation));
+            Assert.IsTrue(keys.Contains(WFConstants.BackendHeaders.SubStatus));
+            Assert.AreEqual(allKeys.Length, keys.Length);
+            Assert.AreEqual(
+                Headers.Get(HttpConstants.HttpHeaders.PartitionKey), 
+                clone.Get(HttpConstants.HttpHeaders.PartitionKey));
+            Assert.AreEqual(
+                Headers.Get(HttpConstants.HttpHeaders.RetryAfterInMilliseconds), 
+                clone.Get(HttpConstants.HttpHeaders.RetryAfterInMilliseconds));
+            Assert.AreEqual(
+                Headers.Get(HttpConstants.HttpHeaders.Continuation),
+                clone.Get(HttpConstants.HttpHeaders.Continuation));
+            Assert.AreEqual(
+                Headers.Get(WFConstants.BackendHeaders.SubStatus),
+                clone.Get(WFConstants.BackendHeaders.SubStatus));
+        }
+
+        [TestMethod]
+        public void TestNullHeadersClone()
+        {
+            Headers Headers = new Headers();
+            Headers.CosmosMessageHeaders[Key] = Guid.NewGuid().ToString();
+            Headers.ContinuationToken = Guid.NewGuid().ToString();
+            Headers.CosmosMessageHeaders[HttpConstants.HttpHeaders.RetryAfterInMilliseconds] = "20";
+            Headers.Add(WFConstants.BackendHeaders.SubStatus, "1002");
+            Headers.PartitionKey = "pk";
+
+            Headers.CosmosMessageHeaders["x-ms-documentdb-partitionkey"] = null;
+
+            string[] allKeys = Headers.AllKeys();
+            Assert.IsTrue(allKeys.Contains(Key));
+            Assert.IsFalse(allKeys.Contains(HttpConstants.HttpHeaders.PartitionKey));
+            Assert.IsTrue(allKeys.Contains(HttpConstants.HttpHeaders.RetryAfterInMilliseconds));
+            Assert.IsTrue(allKeys.Contains(HttpConstants.HttpHeaders.Continuation));
+            Assert.IsTrue(allKeys.Contains(WFConstants.BackendHeaders.SubStatus));
+
+            Headers clone = Headers.Clone();
+            Assert.IsNotNull(clone);
+            string[] keys = clone.AllKeys();
+            Assert.IsTrue(keys.Contains(Key));
+            Assert.IsFalse(keys.Contains(HttpConstants.HttpHeaders.PartitionKey));
+            Assert.IsTrue(keys.Contains(HttpConstants.HttpHeaders.RetryAfterInMilliseconds));
+            Assert.IsTrue(keys.Contains(HttpConstants.HttpHeaders.Continuation));
+            Assert.IsTrue(keys.Contains(WFConstants.BackendHeaders.SubStatus));
+            Assert.AreEqual(allKeys.Length, keys.Length);
+            Assert.AreEqual(
+                Headers.Get(HttpConstants.HttpHeaders.PartitionKey),
+                clone.Get(HttpConstants.HttpHeaders.PartitionKey));
+            Assert.AreEqual(
+                Headers.Get(HttpConstants.HttpHeaders.RetryAfterInMilliseconds),
+                clone.Get(HttpConstants.HttpHeaders.RetryAfterInMilliseconds));
+            Assert.AreEqual(
+                Headers.Get(HttpConstants.HttpHeaders.Continuation),
+                clone.Get(HttpConstants.HttpHeaders.Continuation));
+            Assert.AreEqual(
+                Headers.Get(WFConstants.BackendHeaders.SubStatus),
+                clone.Get(WFConstants.BackendHeaders.SubStatus));
+        }
     }
 }
\ No newline at end of file