diff --git a/net/blockwise/blockwise.go b/net/blockwise/blockwise.go
index 1828d75e..c828b97e 100644
--- a/net/blockwise/blockwise.go
+++ b/net/blockwise/blockwise.go
@@ -386,6 +386,10 @@ func (b *BlockWise[C]) handleReceivedMessage(w *responsewriter.ResponseWriter[C]
 		next(w, r)
 		return nil
 	case codes.GET, codes.DELETE:
+		// For GET and DELETE requests in CoAP, the initial request cannot have the message type of Acknowledge (ACK) or Reset (RST)
+		if r.Type() == message.Acknowledgement || r.Type() == message.Reset {
+			return fmt.Errorf("invalid message type(%v) for code(%v)", r.Type(), r.Code())
+		}
 		maxSZX = fitSZX(r, message.Block2, maxSZX)
 		block, errG := r.GetOptionUint32(message.Block2)
 		if errG == nil {