diff --git a/libs/color-sensor/color.ts b/libs/color-sensor/color.ts
index 63fcd37f..33f61a2b 100644
--- a/libs/color-sensor/color.ts
+++ b/libs/color-sensor/color.ts
@@ -253,6 +253,11 @@ namespace sensors {
         //% this.fieldEditor="ports"
         //% help=sensors/color-sensor/set-threshold
         setThreshold(condition: Light, value: number) {
+            // threshold is used in ambient or reflected modes
+            if (this.mode != LightIntensityMode.Ambient &&
+                this.mode != LightIntensityMode.Reflected)
+                this.setMode(ColorSensorMode.ReflectedLightIntensity);
+
             if (condition == Light.Dark)
                 this.thresholdDetector.setLowThreshold(value)
             else
@@ -268,7 +273,12 @@ namespace sensors {
         //% this.fieldEditor="ports"
         //% help=sensors/color-sensor/threshold
         threshold(condition: Light): number {
-            return this.thresholdDetector.threshold(<ThresholdState><number>Light.Dark);
+            // threshold is used in ambient or reflected modes
+            if (this.mode != LightIntensityMode.Ambient &&
+                this.mode != LightIntensityMode.Reflected)
+                this.setMode(ColorSensorMode.ReflectedLightIntensity);
+
+            return this.thresholdDetector.threshold(<ThresholdState><number>condition);
         }
 
         /**
diff --git a/libs/infrared-sensor/ir.ts b/libs/infrared-sensor/ir.ts
index bdfbf321..1a11b2eb 100644
--- a/libs/infrared-sensor/ir.ts
+++ b/libs/infrared-sensor/ir.ts
@@ -279,7 +279,7 @@ namespace sensors {
         //% group="Threshold" blockGap=8 weight=49
         //% this.fieldEditor="ports"
         proximityThreshold(condition: InfraredSensorEvent): number {
-            return this._proximityThreshold.threshold(<ThresholdState><number>Light.Dark);
+            return this._proximityThreshold.threshold(<ThresholdState><number>condition);
         }
 
         // TODO
diff --git a/libs/ultrasonic-sensor/ultrasonic.ts b/libs/ultrasonic-sensor/ultrasonic.ts
index 42d4e05c..f0a1c13b 100644
--- a/libs/ultrasonic-sensor/ultrasonic.ts
+++ b/libs/ultrasonic-sensor/ultrasonic.ts
@@ -115,8 +115,8 @@ namespace sensors {
         //% this.fieldEditor="ports"
         threshold(condition: UltrasonicSensorEvent): number {
             switch (condition) {
-                case UltrasonicSensorEvent.ObjectNear: this.promixityThreshold.threshold(ThresholdState.Low); break;
-                case UltrasonicSensorEvent.ObjectDetected: this.movementThreshold; break;
+                case UltrasonicSensorEvent.ObjectNear: return this.promixityThreshold.threshold(ThresholdState.Low);
+                case UltrasonicSensorEvent.ObjectDetected: return this.movementThreshold;
             }
             return 0;
         }