diff --git a/ampel-firmware/lorawan.cpp b/ampel-firmware/lorawan.cpp
index 99b3c4b9ae98297c7dbc91114e689a6e5c24797d..c7302e73274e93156b9d0fe9402d9ff687bcc81f 100644
--- a/ampel-firmware/lorawan.cpp
+++ b/ampel-firmware/lorawan.cpp
@@ -80,9 +80,9 @@ namespace lorawan {
   void onEvent(ev_t ev) {
     char current_time[23];
     ntp::getLocalTime(current_time);
-    Serial.print("LoRa - ");
+    Serial.print(F("LoRa - "));
     Serial.print(current_time);
-    Serial.print(" - ");
+    Serial.print(F(" - "));
     switch (ev) {
     case EV_JOINING:
       Serial.println(F("EV_JOINING"));