Index: generic/predefined.h
===================================================================
diff -u -r35e0efc0d8851a10c70071c12112b11538ce97af -raa1943604c4de3d538dff67d5e9e238323d37474
--- generic/predefined.h	(.../predefined.h)	(revision 35e0efc0d8851a10c70071c12112b11538ce97af)
+++ generic/predefined.h	(.../predefined.h)	(revision aa1943604c4de3d538dff67d5e9e238323d37474)
@@ -315,7 +315,8 @@
 "proc ::nx::core::parametersFromSlots {obj} {\n"
 "set parameterdefinitions [list]\n"
 "foreach slot [::nx::objectInfo slotobjects $obj] {\n"
-"if {[::nx::core::objectproperty $obj type ::xotcl::Object] &&\n"
+"if {[::nx::core::objectproperty ::xotcl::Object class]\n"
+"&& [::nx::core::objectproperty $obj type ::xotcl::Object] &&\n"
 "([$slot name] eq \"mixin\" || [$slot name] eq \"filter\")} continue\n"
 "array set \"\" [$slot toParameterSyntax]\n"
 "lappend parameterdefinitions -$(oparam)}\n"