diff --git a/lorawan.cpp b/lorawan.cpp
index 9bf74769f3ad1f74ad42d5a0d1114e5357554683..9dc37ff02ed5b541a20908902f621b170fcbf1ba 100644
--- a/lorawan.cpp
+++ b/lorawan.cpp
@@ -183,7 +183,7 @@ namespace lorawan {
     }
   }
 
-  void preparePayloadIfTimeHasCome(int16_t co2, float temperature, float humidity) {
+  void preparePayloadIfTimeHasCome(const int16_t &co2, const float &temperature, const float &humidity) {
     static unsigned long last_sent_at = 0;
     unsigned long now = seconds();
     if (now - last_sent_at > config::lorawan_sending_interval) {