diff --git a/src/core/meshcop/joiner_router.cpp b/src/core/meshcop/joiner_router.cpp
index 0543c9b62..d70e0a7ac 100644
--- a/src/core/meshcop/joiner_router.cpp
+++ b/src/core/meshcop/joiner_router.cpp
@@ -148,6 +148,7 @@ void JoinerRouter::HandleUdpReceive(Message &aMessage, const Ip6::MessageInfo &a
     JoinerRouterLocatorTlv rloc;
     ExtendedTlv            tlv;
     uint16_t               borderAgentRloc;
+    uint16_t               offset;
 
     otLogInfoMeshCoP("JoinerRouter::HandleUdpReceive");
 
@@ -175,22 +176,9 @@ void JoinerRouter::HandleUdpReceive(Message &aMessage, const Ip6::MessageInfo &a
     tlv.SetType(Tlv::kJoinerDtlsEncapsulation);
     tlv.SetLength(aMessage.GetLength() - aMessage.GetOffset());
     SuccessOrExit(error = message->Append(&tlv, sizeof(tlv)));
-
-    while (aMessage.GetOffset() < aMessage.GetLength())
-    {
-        uint16_t length = aMessage.GetLength() - aMessage.GetOffset();
-        uint8_t  tmp[16];
-
-        if (length >= sizeof(tmp))
-        {
-            length = sizeof(tmp);
-        }
-
-        aMessage.Read(aMessage.GetOffset(), length, tmp);
-        aMessage.MoveOffset(length);
-
-        SuccessOrExit(error = message->Append(tmp, length));
-    }
+    offset = message->GetLength();
+    SuccessOrExit(error = message->SetLength(offset + tlv.GetLength()));
+    aMessage.CopyTo(aMessage.GetOffset(), offset, tlv.GetLength(), *message);
 
     messageInfo.SetSockAddr(netif.GetMle().GetMeshLocal16());
     messageInfo.SetPeerAddr(netif.GetMle().GetMeshLocal16());