diff --git a/libs/color-sensor/color.ts b/libs/color-sensor/color.ts
index c1c624c1..391f7c52 100644
--- a/libs/color-sensor/color.ts
+++ b/libs/color-sensor/color.ts
@@ -56,6 +56,7 @@ namespace sensors {
 
         constructor(port: number) {
             super(port)
+            this._setMode(ColorSensorMode.None);
             this.thresholdDetector = new sensors.internal.ThresholdDetector(this.id());
         }
 
@@ -94,7 +95,6 @@ namespace sensors {
         }
 
         _update(prev: number, curr: number) {
-            if (curr == null) return;
             if (this.mode == ColorSensorMode.Color)
                 control.raiseEvent(this._id, this._colorEventValue(curr));
             else
diff --git a/libs/core/input.ts b/libs/core/input.ts
index 896c8a3c..440dfbe8 100644
--- a/libs/core/input.ts
+++ b/libs/core/input.ts
@@ -68,7 +68,7 @@ namespace sensors.internal {
                 if (info.sensor) return info.sensor._query()
                 return 0
             }, (prev, curr) => {
-                if (info.sensor) info.sensor._update(prev, curr)
+                if (info.sensor && curr !== null) info.sensor._update(prev, curr)
             })
         }
 
diff --git a/sim/state/color.ts b/sim/state/color.ts
index ad5f7ac5..47392084 100644
--- a/sim/state/color.ts
+++ b/sim/state/color.ts
@@ -3,12 +3,13 @@
 namespace pxsim {
 
     export enum ColorSensorMode {
+        None = -1,
         Reflected = 0,
         Ambient = 1,
         Colors = 2,
         RefRaw = 3,
         RgbRaw = 4,
-        ColorCal = 5
+        ColorCal = 5,
     }
 
     export enum ThresholdState {
@@ -24,6 +25,7 @@ namespace pxsim {
 
         constructor(port: number) {
             super(port);
+            this.mode = -1;
         }
 
         getDeviceType() {