diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/entities/AbstractActivitySample.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/entities/AbstractActivitySample.java
index 07fdf0111..4c7516844 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/entities/AbstractActivitySample.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/entities/AbstractActivitySample.java
@@ -69,7 +69,7 @@ public abstract class AbstractActivitySample implements ActivitySample {
 
     @Override
     public Integer getHeartRate() {
-        return null;
+        return NOT_MEASURED;
     }
 
     public abstract void setDeviceId(long deviceId);
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/model/ActivitySample.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/model/ActivitySample.java
index 2e017678d..b0d15b014 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/model/ActivitySample.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/model/ActivitySample.java
@@ -77,7 +77,7 @@ public interface ActivitySample extends TimeStamped {
      * The value is returned in heart beats per minute, in the range from
      * 0-255, where 255 is an illegal value (e.g. due to a bad measurement)
      *
-     * @return the heart rate value in beats per minute, or null if none
+     * @return the heart rate value in beats per minute, or -1 if none
      */
     Integer getHeartRate();