diff --git a/src/core/meshcop/dataset_manager.cpp b/src/core/meshcop/dataset_manager.cpp
index 8d5d67f96..12a68f5ad 100644
--- a/src/core/meshcop/dataset_manager.cpp
+++ b/src/core/meshcop/dataset_manager.cpp
@@ -334,6 +334,7 @@ ThreadError DatasetManager::Set(Coap::Header &aHeader, Message &aMessage, const
 
     ActiveTimestampTlv activeTimestamp;
     NetworkMasterKeyTlv masterKey;
+    ChannelTlv channel;
 
     activeTimestamp.SetLength(0);
     masterKey.SetLength(0);
@@ -364,6 +365,11 @@ ThreadError DatasetManager::Set(Coap::Header &aHeader, Message &aMessage, const
             aMessage.Read(offset, sizeof(masterKey), &masterKey);
             break;
 
+        case Tlv::kChannel:
+            aMessage.Read(offset, sizeof(channel), &channel);
+            VerifyOrExit(channel.GetChannel() >= kPhyMinChannel && channel.GetChannel() <= kPhyMaxChannel,
+                         state = StateTlv::kReject);
+
         default:
             break;
         }
@@ -544,10 +550,30 @@ ThreadError DatasetManager::SendSetRequest(const otOperationalDataset &aDataset,
 
     if (isCommissioner)
     {
-        CommissionerSessionIdTlv sessionId;
-        sessionId.Init();
-        sessionId.SetCommissionerSessionId(mNetif.GetCommissioner().GetSessionId());
-        SuccessOrExit(error = message->Append(&sessionId, sizeof(sessionId)));
+        const uint8_t *cur = aTlvs;
+        const uint8_t *end = aTlvs + aLength;
+        bool hasSessionId = false;
+
+        while (cur < end)
+        {
+            const Tlv *data = reinterpret_cast<const Tlv *>(cur);
+
+            if (data->GetType() == Tlv::kCommissionerSessionId)
+            {
+                hasSessionId = true;
+                break;
+            }
+
+            cur += sizeof(Tlv) + data->GetLength();
+        }
+
+        if (!hasSessionId)
+        {
+            CommissionerSessionIdTlv sessionId;
+            sessionId.Init();
+            sessionId.SetCommissionerSessionId(mNetif.GetCommissioner().GetSessionId());
+            SuccessOrExit(error = message->Append(&sessionId, sizeof(sessionId)));
+        }
     }
 
 #endif
diff --git a/tools/harness-thci/ARM.py b/tools/harness-thci/ARM.py
index 5f6653275..ce4685a77 100644
--- a/tools/harness-thci/ARM.py
+++ b/tools/harness-thci/ARM.py
@@ -2193,7 +2193,10 @@ class ARM(IThci):
 
             if listChannelMask != None:
                 cmd += ' channelmask '
-                cmd += str(hex(1 << listChannelMask[1]))
+                if len(listChannelMask) > 2:
+                    cmd += '0x' + self.__convertLongToString(self.__convertChannelMask(listChannelMask))
+                elif len(listChannelMask) == 2:
+                    cmd += str(hex(1 << listChannelMask[1]))
 
             if sPSKc != None or listSecurityPolicy != None or \
                xCommissioningSessionId != None or xTmfPort != None or xSteeringData != None or xBorderRouterLocator != None or \
@@ -2251,6 +2254,14 @@ class ARM(IThci):
 
                 cmd += locator
 
+            if xSteeringData != None:
+                steeringData = self.__convertLongToString(xSteeringData)
+                cmd += '08' + str(len(steeringData)/2).zfill(2)
+                cmd += steeringData
+
+            if BogusTLV != None:
+                cmd += "8202aa55"
+
             print cmd
 
             return self.__sendCommand(cmd)[0] == 'Done'