diff --git a/firmware/controllers/algo/engine.cpp b/firmware/controllers/algo/engine.cpp
index 15394cf410..494d30a805 100644
--- a/firmware/controllers/algo/engine.cpp
+++ b/firmware/controllers/algo/engine.cpp
@@ -184,7 +184,7 @@ TransmissionState::TransmissionState() {
 }
 
 EngineState::EngineState() {
-	dwellAngle = 0;
+	dwellAngle = NAN;
 	engineNoiseHipLevel = 0;
 	injectorLag = 0;
 	warningCounter = 0;
@@ -231,7 +231,7 @@ void EngineState::periodicFastCallback(DECLARE_ENGINE_PARAMETER_SIGNATURE) {
 
 	int rpm = ENGINE(rpmCalculator).getRpm(PASS_ENGINE_PARAMETER_SIGNATURE);
 	sparkDwell = getSparkDwell(rpm PASS_ENGINE_PARAMETER_SUFFIX);
-	dwellAngle = sparkDwell / getOneDegreeTimeMs(rpm);
+	dwellAngle = cisnan(rpm) ? NAN :  sparkDwell / getOneDegreeTimeMs(rpm);
 	if (hasAfrSensor(PASS_ENGINE_PARAMETER_SIGNATURE)) {
 		engine->sensors.currentAfr = getAfr(PASS_ENGINE_PARAMETER_SIGNATURE);
 	}
diff --git a/firmware/controllers/algo/engine.h b/firmware/controllers/algo/engine.h
index 28567bb09f..129f6b71b1 100644
--- a/firmware/controllers/algo/engine.h
+++ b/firmware/controllers/algo/engine.h
@@ -166,6 +166,7 @@ public:
 
 	/**
 	 * ignition dwell duration as crankshaft angle
+	 * NAN if engine is stopped
 	 */
 	angle_t dwellAngle;