diff --git a/src/core/coap/coap.hpp b/src/core/coap/coap.hpp
index 4e35dd1bb..14bac1f81 100644
--- a/src/core/coap/coap.hpp
+++ b/src/core/coap/coap.hpp
@@ -485,14 +485,6 @@ public:
      */
     otError Stop(void);
 
-    /**
-     * This method returns a port number used by CoAP service.
-     *
-     * @returns A port number.
-     *
-     */
-    uint16_t GetPort(void) { return mSocket.GetSockName().mPort; };
-
     /**
      * This method adds a resource to the CoAP server.
      *
diff --git a/src/core/meshcop/joiner.cpp b/src/core/meshcop/joiner.cpp
index 58950e95c..7b959d8cd 100644
--- a/src/core/meshcop/joiner.cpp
+++ b/src/core/meshcop/joiner.cpp
@@ -159,7 +159,7 @@ void Joiner::Close(void)
     ThreadNetif &netif = GetNetif();
 
     netif.GetCoapSecure().Disconnect();
-    netif.GetIp6Filter().RemoveUnsecurePort(netif.GetCoapSecure().GetPort());
+    netif.GetIp6Filter().RemoveUnsecurePort(OPENTHREAD_CONFIG_JOINER_UDP_PORT);
 }
 
 void Joiner::Complete(otError aError)
@@ -290,7 +290,7 @@ otError Joiner::TryNextJoin()
 
         netif.GetMac().SetPanId(joinerRouter->mPanId);
         netif.GetMac().SetPanChannel(joinerRouter->mChannel);
-        netif.GetIp6Filter().AddUnsecurePort(netif.GetCoapSecure().GetPort());
+        netif.GetIp6Filter().AddUnsecurePort(OPENTHREAD_CONFIG_JOINER_UDP_PORT);
 
         messageInfo.GetPeerAddr().mFields.m16[0] = HostSwap16(0xfe80);
         messageInfo.GetPeerAddr().SetIid(joinerRouter->mExtAddr);