NSTokenField in Xcode

I’m trying to change the default separator character for a NSTokenField with this:

	 on applicationDidFinishLaunching:aNotification
		set theSet to current application's NSCharacterSet's characterSetWithCharactersInString:space
		theToken's tokenizingCharacterSet:theSet
	 end applicationDidFinishLaunching:

I’m getting this error:
[AppDelegate applicationDidFinishLaunching:]: -[NSTokenField tokenizingCharacterSet:]: unrecognized selector sent to instance 0x104304b00 (error -10000)

What’s wrong?

MacOS 10.11.6 (15G20015)
Script Debugger 6.0.8 (6A225)
Xcode 8.2.1 (11766.1)

You mean:

		theToken's setTokenizingCharacterSet:theSet

Sometimes, I feel stupid!