Index: generic/predefined.h
===================================================================
diff -u -r7c35873dabef0d6f513e3c9b6844dacfd7574277 -rc74faac63d3cf530ab8fee0fb2bb2226a107cd31
--- generic/predefined.h	(.../predefined.h)	(revision 7c35873dabef0d6f513e3c9b6844dacfd7574277)
+++ generic/predefined.h	(.../predefined.h)	(revision c74faac63d3cf530ab8fee0fb2bb2226a107cd31)
@@ -241,7 +241,7 @@
 "error \"Property $prop of ${.domain}->$obj ist not multivalued\"}\n"
 "set perObject [expr {${per-object} ? \"-per-object\" : \"\"}]\n"
 "set oldSetting [::xotcl::relation $obj {*}$perObject $prop]\n"
-"$obj $prop {*}$perObject [linsert $oldSetting $pos $value]}\n"
+"::xotcl::relation $obj {*}$perObject $prop [linsert $oldSetting $pos $value]}\n"
 "proc ::xotcl::register_system_slots {os} {\n"
 "${os}::Object alloc ${os}::Class::slot\n"
 "${os}::Object alloc ${os}::Object::slot\n"
Index: generic/predefined.xotcl
===================================================================
diff -u -r7c35873dabef0d6f513e3c9b6844dacfd7574277 -rc74faac63d3cf530ab8fee0fb2bb2226a107cd31
--- generic/predefined.xotcl	(.../predefined.xotcl)	(revision 7c35873dabef0d6f513e3c9b6844dacfd7574277)
+++ generic/predefined.xotcl	(.../predefined.xotcl)	(revision c74faac63d3cf530ab8fee0fb2bb2226a107cd31)
@@ -469,7 +469,7 @@
   }
   set perObject [expr {${per-object} ? "-per-object" : ""}]
   set oldSetting [::xotcl::relation $obj {*}$perObject $prop]
-  $obj $prop {*}$perObject [linsert $oldSetting $pos $value]
+  ::xotcl::relation $obj {*}$perObject $prop [linsert $oldSetting $pos $value]
 }
 
 ############################################
@@ -484,7 +484,6 @@
   ::xotcl::InfoSlot create ${os}::Object::slot::class -type relation
   ::xotcl::alias           ${os}::Object::slot::class assign ::xotcl::relation
 
-
   ::xotcl::InterceptorSlot create ${os}::Object::slot::mixin \
       -type relation
 
Index: tests/interceptor-slot.xotcl
===================================================================
diff -u -re591522c92d208c4942888e632546262fd7641ad -rc74faac63d3cf530ab8fee0fb2bb2226a107cd31
--- tests/interceptor-slot.xotcl	(.../interceptor-slot.xotcl)	(revision e591522c92d208c4942888e632546262fd7641ad)
+++ tests/interceptor-slot.xotcl	(.../interceptor-slot.xotcl)	(revision c74faac63d3cf530ab8fee0fb2bb2226a107cd31)
@@ -32,8 +32,14 @@
 C mixin delete M2
 ? {c1 info precedence} "::M ::C ::xotcl2::Object"
 C mixin delete M
+# per-object mixins
 ? {c1 info precedence} "::C ::xotcl2::Object"
 c1 mixin add M
+? {::xotcl::relation c1 mixin} ::M
+? {catch {c1 mixin UNKNWON}} 1
+# after an error in mixin, the list is reset to empty. Wanted?
+? {::xotcl::relation c1 mixin} ""
+c1 mixin add M
 ? {c1 info precedence} "::M ::C ::xotcl2::Object"
 c1 mixin add M2
 ? {c1 info precedence} "::M2 ::M ::C ::xotcl2::Object"
@@ -42,6 +48,7 @@
 c1 mixin delete M2
 ? {c1 info precedence} "::C ::xotcl2::Object"
 
+
 #
 # adding, removing per-object mixins for classes through relation 
 #
@@ -56,6 +63,10 @@
 #
 C mixin -per-object add M 
 ? {C info precedence} "::M ::xotcl2::Class ::xotcl2::Object"
+? {::xotcl::relation C -per-object mixin} ::M
+# is the following wanted?
+? {catch {C mixin -per-object add UNKNWON}} 1
+? {::xotcl::relation C -per-object mixin} ""
 C mixin -per-object ""
 ? {C info precedence} "::xotcl2::Class ::xotcl2::Object"