diff --git a/ampel-firmware/co2_sensor.cpp b/ampel-firmware/co2_sensor.cpp
index e88dc93256ddbe249375bbbc7b75c0204d4c1b72..93eb1da4d2fe7355c6142d3c8b0d3f3a6251caac 100644
--- a/ampel-firmware/co2_sensor.cpp
+++ b/ampel-firmware/co2_sensor.cpp
@@ -41,7 +41,7 @@ namespace sensor {
     BOOTUP,
     READY,
     NEEDS_CALIBRATION,
-    PREPARE_CALIBRATION_INSTABLE,
+    PREPARE_CALIBRATION_UNSTABLE,
     PREPARE_CALIBRATION_STABLE,
     CALIBRATION
   };
@@ -50,7 +50,7 @@ namespace sensor {
       "BOOTUP",
       "READY",
       "NEEDS_CALIBRATION",
-      "PREPARE_CALIBRATION_INSTABLE",
+      "PREPARE_CALIBRATION_UNSTABLE",
       "PREPARE_CALIBRATION_STABLE",
       "CALIBRATION" };
   state current_state = INITIAL;
@@ -133,7 +133,7 @@ namespace sensor {
       switchState(PREPARE_CALIBRATION_STABLE);
     } else {
       stable_measurements = 0;
-      switchState(PREPARE_CALIBRATION_INSTABLE);
+      switchState(PREPARE_CALIBRATION_UNSTABLE);
     }
     previous_co2 = co2;
     return (stable_measurements == config::enough_stable_measurements);
@@ -148,7 +148,7 @@ namespace sensor {
     scd30.setMeasurementInterval(2); // [s] The change will only take effect after next measurement.
     Serial.println(F("Waiting until the measurements are stable for at least 2 minutes."));
     Serial.println(F("It could take a very long time."));
-    switchState(PREPARE_CALIBRATION_INSTABLE);
+    switchState(PREPARE_CALIBRATION_UNSTABLE);
   }
 
   void calibrateAndRestart() {
@@ -210,7 +210,7 @@ namespace sensor {
     case NEEDS_CALIBRATION:
       led_effects::showWaitingLED(color::magenta);
       break;
-    case PREPARE_CALIBRATION_INSTABLE:
+    case PREPARE_CALIBRATION_UNSTABLE:
       led_effects::showWaitingLED(color::red);
       break;
     case PREPARE_CALIBRATION_STABLE:
@@ -243,7 +243,7 @@ namespace sensor {
         // zero ppm but non-zero temperature and non-zero humidity.
         Serial.println(F("Invalid sensor data - CO2 concentration <= 0 ppm"));
         switchState(BOOTUP);
-      } else if ((current_state == PREPARE_CALIBRATION_INSTABLE) || (current_state == PREPARE_CALIBRATION_STABLE)) {
+      } else if ((current_state == PREPARE_CALIBRATION_UNSTABLE) || (current_state == PREPARE_CALIBRATION_STABLE)) {
         // Check for pre-calibration states first, because we do not want to
         // leave them before calibration is done.
         bool ready_for_calibration = countStableMeasurements();