[Zope] <dtml-in> problem with defined or not defined variable as parameter

Hi, I want to do something like that: <dtml-if id_historie> <dtml-in expr="dbSelect(id_historie=_.str(id_historie))"> <dtml-else> <dtml-in expr="dbSelect(id_historie=_.str(0))"> <dtml-if> [...] </dtml-in> but I get the error " unexpected end tag, for tag </dtml-in>". How can I query my database depending on having id_historie defined or not? Can somebody give me a hint? Thanks, Patrick