Disambiguation issue

Does anyone have an idea why this does not result in a tag added to an apostrophe? The output suggests it has been touched by disambiguation, but the postag is not there…

	<rule id="APOSTROF" name="">
        <pattern><token>'</token></pattern>
		<disambig action="add" postag="START" />
	</rule>	

'Hij loopt naar school.
Analyzed token readings: [/SENT_START*] ‘[’/null*] Hij[hij/VNW:PER:3EP:EKV:ACT*] [ /null*] loopt[lopen/WKW:TGW:3EP] [ /null*] naar[naar/BNW:STL:ONV,naar/VGW,naar/VRZ] [ /null*] school[sc

Ah, I had to make a new entry first…