diff --git a/util/mqtt.go b/util/mqtt.go
index 0959d99..0c263de 100644
--- a/util/mqtt.go
+++ b/util/mqtt.go
@@ -49,7 +49,7 @@ func init() {
 
 func SendMqttPopInitMessagesToServer(ctx sdk.Context, challenge types.Challenge) {
 	// PoP can only be executed if at least two actors are available.
-	if challenge.Challenger != "" && challenge.Challengee != "" {
+	if challenge.Challenger == "" || challenge.Challengee == "" {
 		return
 	}
 	err := sendMqttPopInitMessages(challenge)