Executing viewmodels command on enter in TextBox

I want to execute a command in my viewmodel when the user presses enter in a TextBox. The command works when bound to a button.

<Button Content="Add" Command="{Binding Path=AddCommand}" />

But I can't bring it to work from the TextBox. I tried an Inputbinding, but it didn't work.

<TextBox.InputBindings>
    <KeyBinding Command="{Binding Path=AddCommand}" Key="Enter"/>
</TextBox.InputBindings>

I also tried to set the working button as default, but it doesn't get executed when enter is pressed.

Thanks for your help.