diff --git a/src/core/coap/coap.cpp b/src/core/coap/coap.cpp
index e402c74ba..1bedbaccf 100644
--- a/src/core/coap/coap.cpp
+++ b/src/core/coap/coap.cpp
@@ -331,6 +331,7 @@ void CoapBase::HandleRetransmissionTimer(void)
                 messageInfo.SetPeerAddr(coapMetadata.mDestinationAddress);
                 messageInfo.SetPeerPort(coapMetadata.mDestinationPort);
                 messageInfo.SetSockAddr(coapMetadata.mSourceAddress);
+                messageInfo.SetInterfaceId(GetNetif().GetInterfaceId());
 
                 SendCopy(*message, messageInfo);
             }