Index: generic/predefined.h
===================================================================
diff -u -r7c5c045a38db603c9a506d17a29403065256a845 -rf9807b1cea03590c9573b5a521760538d53ee90f
--- generic/predefined.h	(.../predefined.h)	(revision 7c5c045a38db603c9a506d17a29403065256a845)
+++ generic/predefined.h	(.../predefined.h)	(revision f9807b1cea03590c9573b5a521760538d53ee90f)
@@ -232,7 +232,7 @@
 "lappend methods $m}\n"
 "error \"Method '$method' unknown for slot [::xotcl::self]; valid are: {[lsort $methods]]}\"}\n"
 "::xotcl::Slot public method destroy {} {\n"
-"if {${.domain} ne \"\"} {\n"
+"if {${.domain} ne \"\" && [::xotcl::is ${.domain} object]} {\n"
 "${.domain} __invalidateobjectparameter}\n"
 "next}\n"
 "::xotcl::Slot method init {args} {\n"