diff --git a/src/main/java/de/dennisguse/opentracks/io/file/exporter/KMLTrackExporter.java b/src/main/java/de/dennisguse/opentracks/io/file/exporter/KMLTrackExporter.java
index a1c47c685..833e9592d 100644
--- a/src/main/java/de/dennisguse/opentracks/io/file/exporter/KMLTrackExporter.java
+++ b/src/main/java/de/dennisguse/opentracks/io/file/exporter/KMLTrackExporter.java
@@ -68,7 +68,7 @@ public class KMLTrackExporter implements TrackExporter {
     public static final String EXTENDED_DATA_TYPE_SPEED = "speed";
     public static final String EXTENDED_DATA_TYPE_DISTANCE = "distance";
     public static final String EXTENDED_DATA_TYPE_CADENCE = "cadence";
-    public static final String EXTENDED_DATA_TYPE_HEART_RATE = "heart_rate";
+    public static final String EXTENDED_DATA_TYPE_HEARTRATE = "heartrate";
     public static final String EXTENDED_DATA_TYPE_POWER = "power";
     public static final String EXTENDED_DATA_TYPE_ALTITUDE_GAIN = "elevation_gain";
     public static final String EXTENDED_DATA_TYPE_ALTITUDE_LOSS = "elevation_loss";
@@ -253,7 +253,7 @@ public class KMLTrackExporter implements TrackExporter {
         writeSimpleArrayStyle(EXTENDED_DATA_TYPE_SPEED, context.getString(R.string.description_speed_ms));
         writeSimpleArrayStyle(EXTENDED_DATA_TYPE_POWER, context.getString(R.string.description_sensor_power));
         writeSimpleArrayStyle(EXTENDED_DATA_TYPE_CADENCE, context.getString(R.string.description_sensor_cadence));
-        writeSimpleArrayStyle(EXTENDED_DATA_TYPE_HEART_RATE, context.getString(R.string.description_sensor_heart_rate));
+        writeSimpleArrayStyle(EXTENDED_DATA_TYPE_HEARTRATE, context.getString(R.string.description_sensor_heart_rate));
 
         printWriter.println("</Schema>");
     }
@@ -348,7 +348,7 @@ public class KMLTrackExporter implements TrackExporter {
             writeSimpleArraySensorData(cadenceList, EXTENDED_DATA_TYPE_CADENCE);
         }
         if (heartRateList.stream().anyMatch(Objects::nonNull)) {
-            writeSimpleArraySensorData(heartRateList, EXTENDED_DATA_TYPE_HEART_RATE);
+            writeSimpleArraySensorData(heartRateList, EXTENDED_DATA_TYPE_HEARTRATE);
         }
         if (altitudeGainList.stream().anyMatch(Objects::nonNull)) {
             writeSimpleArraySensorData(altitudeGainList, EXTENDED_DATA_TYPE_ALTITUDE_GAIN);
diff --git a/src/main/java/de/dennisguse/opentracks/io/file/importer/KmlTrackImporter.java b/src/main/java/de/dennisguse/opentracks/io/file/importer/KmlTrackImporter.java
index 457388b41..31895ffbf 100644
--- a/src/main/java/de/dennisguse/opentracks/io/file/importer/KmlTrackImporter.java
+++ b/src/main/java/de/dennisguse/opentracks/io/file/importer/KmlTrackImporter.java
@@ -82,6 +82,8 @@ public class KmlTrackImporter extends DefaultHandler implements XMLImporter.Trac
     private static final String TAG_UUID = "opentracks:trackid";
 
     private static final String ATTRIBUTE_NAME = "name";
+    // Until v4.13.0, was in contradiction with KML2.3 standard; keeping backward compatibility.
+    public static final String EXTENDED_DATA_TYPE_HEART_RATE_LEGACY = "heart_rate";
 
     private Locator locator;
 
@@ -426,7 +428,8 @@ public class KmlTrackImporter extends DefaultHandler implements XMLImporter.Trac
             case KMLTrackExporter.EXTENDED_DATA_TYPE_SPEED -> sensorSpeedList.add(value);
             case KMLTrackExporter.EXTENDED_DATA_TYPE_DISTANCE -> sensorDistanceList.add(value);
             case KMLTrackExporter.EXTENDED_DATA_TYPE_POWER -> sensorPowerList.add(value);
-            case KMLTrackExporter.EXTENDED_DATA_TYPE_HEART_RATE -> sensorHeartRateList.add(value);
+            case KMLTrackExporter.EXTENDED_DATA_TYPE_HEARTRATE,
+                 EXTENDED_DATA_TYPE_HEART_RATE_LEGACY -> sensorHeartRateList.add(value);
             case KMLTrackExporter.EXTENDED_DATA_TYPE_CADENCE -> sensorCadenceList.add(value);
             case KMLTrackExporter.EXTENDED_DATA_TYPE_ALTITUDE_GAIN -> altitudeGainList.add(value);
             case KMLTrackExporter.EXTENDED_DATA_TYPE_ALTITUDE_LOSS -> altitudeLossList.add(value);