diff --git a/integration/watermill/gtm/publisher.go b/integration/watermill/gtm/publisher.go
index 2b6f5d7..37523e7 100644
--- a/integration/watermill/gtm/publisher.go
+++ b/integration/watermill/gtm/publisher.go
@@ -2,6 +2,7 @@ package gtm
 
 import (
 	"encoding/json"
+	"fmt"
 	"net/http"
 
 	"github.com/ThreeDotsLabs/watermill/message"
@@ -83,19 +84,20 @@ func (p *Publisher) Publish(topic string, messages ...*message.Message) error {
 			return err
 		}
 
+		// NOTE: `richsstsse` seems to be last parameter in the query to let's ensure it stays that way
 		var richsstsse bool
 		if values.Has("richsstsse") {
-			values.Del("richsstsse")
 			richsstsse = true
+			values.Del("richsstsse")
 		}
 
-		u := p.url + "?"
+		url := fmt.Sprintf("%s?%s", p.url, values.Encode())
 
 		if richsstsse {
-			u += "&richsstsse"
+			url += "&richsstsse"
 		}
 
-		req, err := http.NewRequestWithContext(msg.Context(), http.MethodPost, u, body)
+		req, err := http.NewRequestWithContext(msg.Context(), http.MethodPost, url, body)
 		if err != nil {
 			return errors.Wrap(err, "failed to create request")
 		}
diff --git a/measurementprotocol/v2/unmarshal.go b/measurementprotocol/v2/unmarshal.go
index 0c36d42..1c1dec3 100644
--- a/measurementprotocol/v2/unmarshal.go
+++ b/measurementprotocol/v2/unmarshal.go
@@ -25,6 +25,13 @@ const (
 type Data map[string]any
 
 func Marshal(input *Event) (url.Values, io.Reader, error) {
+	var richsstsse bool
+	// NOTE: `richsstsse` seems to be last parameter in the query to let's ensure it stays that way
+	if input.Richsstsse != nil {
+		richsstsse = true
+		input.Richsstsse = nil
+	}
+
 	a, err := json.Marshal(input)
 	if err != nil {
 		return nil, nil, err
@@ -66,13 +73,22 @@ func Marshal(input *Event) (url.Values, io.Reader, error) {
 
 	var body []string
 	var reader io.Reader
-	for len(ret.Encode()) > 2048 {
+	maxQueryLength := 2048 //
+	if richsstsse {
+		maxQueryLength -= len("&richsstsse")
+	}
+	for len(ret.Encode()) > maxQueryLength {
 		for s, i := range ret {
 			ret.Del(s)
 			body = append(body, s+"="+i[0])
 			break
 		}
 	}
+
+	if richsstsse {
+		ret.Add("richsstsse", "")
+	}
+
 	if len(body) > 0 {
 		reader = bytes.NewReader([]byte(strings.Join(body, "&")))
 	}