diff --git a/ampel-firmware/led_effects.cpp b/ampel-firmware/led_effects.cpp
index 88b0f90c6b1d61b72d468b0172fa1977ad567dd2..f654e77e581ec88bfce7c3dd8be9b648740e9583 100644
--- a/ampel-firmware/led_effects.cpp
+++ b/ampel-firmware/led_effects.cpp
@@ -146,7 +146,7 @@ namespace led_effects {
     pixels.show();
   }
 
-  void showRainbowWheel(int duration_ms, uint16_t hue_increment) {
+  void showRainbowWheel(uint16_t duration_ms, uint16_t hue_increment) {
     if (config::night_mode) {
       return;
     }
diff --git a/ampel-firmware/led_effects.h b/ampel-firmware/led_effects.h
index 03aee3dc24a02dc403b0e20105c3013f678488e5..d34a9bfb7d42eeca5fd8cf0ca55b037dec604482 100644
--- a/ampel-firmware/led_effects.h
+++ b/ampel-firmware/led_effects.h
@@ -29,7 +29,7 @@ namespace led_effects {
   int countdownToZero();
   void showWaitingLED(uint32_t color);
   void showKITTWheel(uint32_t color, uint16_t duration_s = 2);
-  void showRainbowWheel(int duration_ms = 1000, uint16_t hue_increment = 50);
+  void showRainbowWheel(uint16_t duration_ms = 1000, uint16_t hue_increment = 50);
   void displayCO2color(uint16_t co2);
 }
 #endif