ProgressBar binding problem on WP

I'm binding a Progressbar to a property of type double (between 0 and 1) in my viewModel. On android it works ok but on Windows Phone it doesn't update.

<Label Text="{Binding DistanceLeft}" Font="Small" Grid.Column="3" Grid.Row="0" VerticalOptions="CenterAndExpand" HorizontalOptions="End"/>
 <ProgressBar Progress="{Binding DistanceLeftToProgress}" Grid.Column="1" Grid.Row="1" Grid.ColumnSpan="3" VerticalOptions="CenterAndExpand"/>

[JsonProperty(PropertyName = "distanceLeft")]
 public string DistanceLeft { get { return distanceLeft; } set { SetProperty(ref distanceLeft, value); DistanceLeftToProgress = ValueConverter.ConvertDistanceStringToDeviceProgress(value);} }
 public double DistanceLeftToProgress { get { return distanceLeftToProgress; } set { SetProperty(ref distanceLeftToProgress, value); } }

The Label is updated when DistanceLeft is changed. The progressbar only starts with it's correct initial value but doesn't update.
The progressbar and the label are in a ListView.