diff --git a/src/core/net/ip6.cpp b/src/core/net/ip6.cpp
index c21f6361f..72437dfa6 100644
--- a/src/core/net/ip6.cpp
+++ b/src/core/net/ip6.cpp
@@ -1187,9 +1187,10 @@ start:
             // TCP/UDP shares header uint16_t srcPort, uint16_t dstPort
             SuccessOrExit(error = aMessage.Read(aMessage.GetOffset() + sizeof(uint16_t), dstPort));
             dstPort = HostSwap16(dstPort);
-            if (aMessage.IsLinkSecurityEnabled() && Get<ot::Ip6::Filter>().IsUnsecurePort(dstPort))
+
+            if (aMessage.IsLinkSecurityEnabled() && Get<Filter>().IsUnsecurePort(dstPort))
             {
-                Get<ot::Ip6::Filter>().RemoveUnsecurePort(dstPort);
+                IgnoreError(Get<Filter>().RemoveUnsecurePort(dstPort));
             }
         }
 #endif
@@ -1233,7 +1234,8 @@ start:
 
             SuccessOrExit(error = aMessage.Read(aMessage.GetOffset(), sourcePort));
             sourcePort = HostSwap16(sourcePort);
-            if (Get<ot::Ip6::Filter>().IsUnsecurePort(sourcePort))
+
+            if (Get<Filter>().IsUnsecurePort(sourcePort))
             {
                 aMessage.SetLinkSecurityEnabled(false);
                 otLogInfoIp6("Disabled link security for packet to %s", header.GetDestination().ToString().AsCString());
diff --git a/src/core/net/udp6.cpp b/src/core/net/udp6.cpp
index 6f5227c9e..c4b8e18f6 100644
--- a/src/core/net/udp6.cpp
+++ b/src/core/net/udp6.cpp
@@ -325,7 +325,7 @@ otError Udp::SendTo(SocketHandle &aSocket, Message &aMessage, const MessageInfo
 
 #if OPENTHREAD_CONFIG_PLATFORM_UDP_ENABLE
     if (!IsMlePort(aSocket.mSockName.mPort) &&
-        !(aSocket.mSockName.mPort == ot::Tmf::kUdpPort && aMessage.GetSubType() == Message::kSubTypeJoinerEntrust))
+        !(aSocket.mSockName.mPort == Tmf::kUdpPort && aMessage.GetSubType() == Message::kSubTypeJoinerEntrust))
     {
         SuccessOrExit(error = otPlatUdpSend(&aSocket, &aMessage, &messageInfoLocal));
     }