Index: generic/predefined.xotcl
===================================================================
diff -u -rd70c849219212800fa401c2227796b9a63eadcaf -rf9807b1cea03590c9573b5a521760538d53ee90f
--- generic/predefined.xotcl	(.../predefined.xotcl)	(revision d70c849219212800fa401c2227796b9a63eadcaf)
+++ generic/predefined.xotcl	(.../predefined.xotcl)	(revision f9807b1cea03590c9573b5a521760538d53ee90f)
@@ -460,7 +460,7 @@
 }
 
 ::xotcl::Slot public method destroy {} {
-  if {${.domain} ne ""} {
+  if {${.domain} ne "" && [::xotcl::is ${.domain} object]} {
     ${.domain} __invalidateobjectparameter
   }
   next