diff --git a/ampel-firmware/util.cpp b/ampel-firmware/util.cpp
index b555b1a3ec815938933d16052da002b032d1c314..5ec1556bdb636e409b30ec55fc0941f68e6f8c5e 100644
--- a/ampel-firmware/util.cpp
+++ b/ampel-firmware/util.cpp
@@ -48,13 +48,13 @@ namespace ntp {
   void setLocalTime(int32_t unix_seconds) {
     char time[23];
     timeClient.getFormattedDate(time);
-    Serial.print("Current time : ");
+    Serial.print(F("Current time : "));
     Serial.println(time);
-    Serial.print("Setting UNIX time to : ");
+    Serial.print(F("Setting UNIX time to : "));
     Serial.println(unix_seconds);
     timeClient.setEpochTime(unix_seconds - seconds());
     timeClient.getFormattedDate(time);
-    Serial.print("Current time : ");
+    Serial.print(F("Current time : "));
     Serial.println(time);
   }
 }