Make NSTextField update its bound value when setting its string value programmatically

Make NSTextField update its bound value when setting its string value
programmatically

I have an NSTextField bound to a key in the user defaults. When I press
enter or leave the field the bound value is properly updated (I have an
observer for it). However when I programmatically set the value of the
text field the bound value is not updated. The text field however shows
the new string I set with:
stockField1.stringValue = [sender representedObject];
(it's set from a menu item handler). Is it necessary to send an additional
message to the text field or how else can I make this work?