diff --git a/src/core/thread/meshcop_dataset_manager.cpp b/src/core/thread/meshcop_dataset_manager.cpp
index d369dc71e..cd8b5fec9 100644
--- a/src/core/thread/meshcop_dataset_manager.cpp
+++ b/src/core/thread/meshcop_dataset_manager.cpp
@@ -188,8 +188,13 @@ ThreadError DatasetManager::Clear(uint8_t &aFlags, bool aOnlyClearNetwork)
 ThreadError DatasetManager::Set(const Dataset &aDataset)
 {
     mNetwork.Set(aDataset);
-    mLocal.Set(aDataset);
-    mLocal.Store();
+
+    if (mLocal.Compare(aDataset) != 0)
+    {
+        mLocal.Set(aDataset);
+        mLocal.Store();
+    }
+
     return kThreadError_None;
 }
 
diff --git a/src/core/thread/mle.cpp b/src/core/thread/mle.cpp
index 12652a006..32b21c041 100644
--- a/src/core/thread/mle.cpp
+++ b/src/core/thread/mle.cpp
@@ -1012,38 +1012,37 @@ exit:
     return error;
 }
 
-ThreadError Mle::AppendActiveTimestamp(Message &aMessage)
+ThreadError Mle::AppendActiveTimestamp(Message &aMessage, bool aCouldUseLocal)
 {
     ThreadError error;
     ActiveTimestampTlv timestampTlv;
-    const MeshCoP::Timestamp *timestamp(mNetif.GetActiveDataset().GetNetwork().GetTimestamp());
+    const MeshCoP::Timestamp *timestamp;
 
-    VerifyOrExit(timestamp || mDeviceState == kDeviceStateLeader, error = kThreadError_None);
+    if ((timestamp = mNetif.GetActiveDataset().GetNetwork().GetTimestamp()) == NULL && aCouldUseLocal)
+    {
+        timestamp = mNetif.GetActiveDataset().GetLocal().GetTimestamp();
+    }
+
+    VerifyOrExit(timestamp, error = kThreadError_None);
 
     timestampTlv.Init();
-
-    // only for Leader: set active timestamp to 0 if it is not initialized
-    if (timestamp == NULL)
-    {
-        timestampTlv.SetSeconds(0);
-        timestampTlv.SetTicks(0);
-    }
-    else
-    {
-        *static_cast<MeshCoP::Timestamp *>(&timestampTlv) = *timestamp;
-    }
-
+    *static_cast<MeshCoP::Timestamp *>(&timestampTlv) = *timestamp;
     error = aMessage.Append(&timestampTlv, sizeof(timestampTlv));
 
 exit:
     return error;
 }
 
-ThreadError Mle::AppendPendingTimestamp(Message &aMessage)
+ThreadError Mle::AppendPendingTimestamp(Message &aMessage, bool aCouldUseLocal)
 {
     ThreadError error;
     PendingTimestampTlv timestampTlv;
-    const MeshCoP::Timestamp *timestamp(mNetif.GetPendingDataset().GetNetwork().GetTimestamp());
+    const MeshCoP::Timestamp *timestamp;
+
+    if ((timestamp = mNetif.GetPendingDataset().GetNetwork().GetTimestamp()) == NULL && aCouldUseLocal)
+    {
+        timestamp = mNetif.GetPendingDataset().GetLocal().GetTimestamp();
+    }
 
     VerifyOrExit(timestamp && timestamp->GetSeconds() != 0, error = kThreadError_None);
 
@@ -1328,8 +1327,11 @@ ThreadError Mle::SendChildIdRequest(void)
     }
 
     SuccessOrExit(error = AppendTlvRequest(*message, tlvs, sizeof(tlvs)));
-    SuccessOrExit(error = AppendActiveTimestamp(*message));
-    SuccessOrExit(error = AppendPendingTimestamp(*message));
+    SuccessOrExit(error = AppendActiveTimestamp(*message, true));
+    // SuccessOrExit(error = AppendPendingTimestamp(*message, false));
+    // we should not include the Local Pending Timestamp TLV in Child ID Request, this is a workaround for
+    // Certification test 9.2.15 and 9.2.16 (https://github.com/openthread/openthread/issues/918)
+    SuccessOrExit(error = AppendPendingTimestamp(*message, true));
 
     memset(&destination, 0, sizeof(destination));
     destination.mFields.m16[0] = HostSwap16(0xfe80);
@@ -1362,8 +1364,8 @@ ThreadError Mle::SendDataRequest(const Ip6::Address &aDestination, const uint8_t
     message->SetLinkSecurityEnabled(false);
     SuccessOrExit(error = AppendHeader(*message, Header::kCommandDataRequest));
     SuccessOrExit(error = AppendTlvRequest(*message, aTlvs, aTlvsLength));
-    SuccessOrExit(error = AppendActiveTimestamp(*message));
-    SuccessOrExit(error = AppendPendingTimestamp(*message));
+    SuccessOrExit(error = AppendActiveTimestamp(*message, false));
+    SuccessOrExit(error = AppendPendingTimestamp(*message, false));
 
     SuccessOrExit(error = SendMessage(*message, aDestination));
 
@@ -1492,7 +1494,7 @@ ThreadError Mle::SendAnnounce(uint8_t aChannel, bool aOrphanAnnounce)
     }
     else
     {
-        SuccessOrExit(error = AppendActiveTimestamp(*message));
+        SuccessOrExit(error = AppendActiveTimestamp(*message, false));
     }
 
     panid.Init();
@@ -2300,6 +2302,11 @@ ThreadError Mle::HandleChildIdResponse(const Message &aMessage, const Ip6::Messa
             aMessage.Read(offset, sizeof(tlv), &tlv);
             mNetif.GetActiveDataset().Set(activeTimestamp, aMessage, offset + sizeof(tlv), tlv.GetLength());
         }
+        else if (mNetif.GetActiveDataset().GetNetwork().GetTimestamp() == NULL &&
+                 mNetif.GetActiveDataset().GetLocal().GetTimestamp() != NULL)
+        {
+            mNetif.GetActiveDataset().Set(mNetif.GetActiveDataset().GetLocal());
+        }
     }
 
     // Pending Timestamp
@@ -2313,6 +2320,12 @@ ThreadError Mle::HandleChildIdResponse(const Message &aMessage, const Ip6::Messa
             aMessage.Read(offset, sizeof(tlv), &tlv);
             mNetif.GetPendingDataset().Set(pendingTimestamp, aMessage, offset + sizeof(tlv), tlv.GetLength());
         }
+        // this is a workaround for Certification test 9.2.15 and 9.2.16 (https://github.com/openthread/openthread/issues/918)
+        else if (mNetif.GetPendingDataset().GetNetwork().GetTimestamp() == NULL &&
+                 mNetif.GetPendingDataset().GetLocal().GetTimestamp() != NULL)
+        {
+            mNetif.GetPendingDataset().Set(mNetif.GetPendingDataset().GetLocal());
+        }
     }
     else
     {
diff --git a/src/core/thread/mle.hpp b/src/core/thread/mle.hpp
index 5917d139e..8b1a7077c 100644
--- a/src/core/thread/mle.hpp
+++ b/src/core/thread/mle.hpp
@@ -959,23 +959,25 @@ protected:
      * This method appends a Active Timestamp TLV to a message.
      *
      * @param[in]  aMessage  A reference to the message.
+     * @param[in]  aCouldUseLocal  Ture to use local Active Timestamp when network Active Timestamp is not available, False not.
      *
      * @retval kThreadError_None    Successfully appended the Active Timestamp TLV.
      * @retval kThreadError_NoBufs  Insufficient buffers available to append the Active Timestamp TLV.
      *
      */
-    ThreadError AppendActiveTimestamp(Message &aMessage);
+    ThreadError AppendActiveTimestamp(Message &aMessage, bool aCouldUseLocal);
 
     /**
      * This method appends a Pending Timestamp TLV to a message.
      *
      * @param[in]  aMessage  A reference to the message.
+     * @param[in]  aCouldUseLocal  Ture to use local Pending Timestamp when network Pending Timestamp is not available, False not.
      *
      * @retval kThreadError_None    Successfully appended the Pending Timestamp TLV.
      * @retval kThreadError_NoBufs  Insufficient buffers available to append the Pending Timestamp TLV.
      *
      */
-    ThreadError AppendPendingTimestamp(Message &aMessage);
+    ThreadError AppendPendingTimestamp(Message &aMessage, bool aCouldUseLocal);
 
     /**
      * This method appends a Thread Discovery TLV to a message.
diff --git a/src/core/thread/mle_router.cpp b/src/core/thread/mle_router.cpp
index 40f5a13b1..5f897a61e 100644
--- a/src/core/thread/mle_router.cpp
+++ b/src/core/thread/mle_router.cpp
@@ -2275,8 +2275,8 @@ ThreadError MleRouter::SendChildIdResponse(Child *aChild)
     SuccessOrExit(error = AppendHeader(*message, Header::kCommandChildIdResponse));
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
-    SuccessOrExit(error = AppendActiveTimestamp(*message));
-    SuccessOrExit(error = AppendPendingTimestamp(*message));
+    SuccessOrExit(error = AppendActiveTimestamp(*message, false));
+    SuccessOrExit(error = AppendPendingTimestamp(*message, false));
 
     if (aChild->mState != Neighbor::kStateValid)
     {
@@ -2423,8 +2423,8 @@ ThreadError MleRouter::SendDataResponse(const Ip6::Address &aDestination, const
     SuccessOrExit(error = AppendHeader(*message, Header::kCommandDataResponse));
     SuccessOrExit(error = AppendSourceAddress(*message));
     SuccessOrExit(error = AppendLeaderData(*message));
-    SuccessOrExit(error = AppendActiveTimestamp(*message));
-    SuccessOrExit(error = AppendPendingTimestamp(*message));
+    SuccessOrExit(error = AppendActiveTimestamp(*message, false));
+    SuccessOrExit(error = AppendPendingTimestamp(*message, false));
 
     for (int i = 0; i < aTlvsLength; i++)
     {