Gtk-WARNING: Failed to set property GtkBox.homogeneous

When I launch the builder from the command line I'm getting this error:

(gnome-builder:2): Gtk-WARNING **: 09:31:08.157: Failed to set property GtkBox.homogeneous to cierto: Could not parse boolean 'cierto'

This is because there's a translatable property in a .ui file that should be true or false but it's translated:

I think that a context is needed.