Index: TODO
===================================================================
diff -u -rabcb5e0cd5c1c27262daf76ab309e9c1f18f5ed5 -r5e70792b640c7d8b9a7235ba529dbfc0af2b84ad
--- TODO	(.../TODO)	(revision abcb5e0cd5c1c27262daf76ab309e9c1f18f5ed5)
+++ TODO	(.../TODO)	(revision 5e70792b640c7d8b9a7235ba529dbfc0af2b84ad)
@@ -1237,6 +1237,9 @@
 - removed objectproperty, replaced it by ::nsf::is
 - move functionalizy of objectproperty to make "obj info is ..." more efficient
 
+- report "invalid parameter" in nsf::is and parametercheck, even when
+  no-complain is used.
+
 TODO: 
 - reflect changes in /is/objectproperty/info has/info is/ in migration guide
 - implement built-in-converter for "baseclass" and "metaclass"?
Index: generic/xotcl.c
===================================================================
diff -u -rd9b42d77f43db84a9983cc3bbc4124cf0b52df29 -r5e70792b640c7d8b9a7235ba529dbfc0af2b84ad
--- generic/xotcl.c	(.../xotcl.c)	(revision d9b42d77f43db84a9983cc3bbc4124cf0b52df29)
+++ generic/xotcl.c	(.../xotcl.c)	(revision 5e70792b640c7d8b9a7235ba529dbfc0af2b84ad)
@@ -12682,10 +12682,16 @@
 
   result = Parametercheck(interp, objPtr, valueObj, "value:", &paramPtr);
 
-  /*fprintf(stderr, "after convert\n");*/
+  if (paramPtr == NULL) {
+    /* 
+     * We could not convert the arguments. Even with noComplain, we
+     * report the invalid converter spec as exception
+     */
+    return TCL_ERROR;
+  }
 
-  if (paramPtr && paramPtr->converter == convertViaCmd && 
-      (withNocomplain || result == TCL_OK)) {
+  if (paramPtr->converter == convertViaCmd 
+      && (withNocomplain || result == TCL_OK)) {
     Tcl_ResetResult(interp);
   } 
 
Index: tests/parameters.tcl
===================================================================
diff -u -rabcb5e0cd5c1c27262daf76ab309e9c1f18f5ed5 -r5e70792b640c7d8b9a7235ba529dbfc0af2b84ad
--- tests/parameters.tcl	(.../parameters.tcl)	(revision abcb5e0cd5c1c27262daf76ab309e9c1f18f5ed5)
+++ tests/parameters.tcl	(.../parameters.tcl)	(revision 5e70792b640c7d8b9a7235ba529dbfc0af2b84ad)
@@ -36,6 +36,8 @@
   ? {::nsf::is baseclass C} 0
   ? {C info is baseclass} 0
 
+  ? {::nsf::is class ::nx::Object} 1
+  ? {::nsf::is ::nx::Object class} {invalid value constraints "::nx::Object"}
 
   ? {::nsf::parametercheck object o1} 1
   ? {::nsf::parametercheck -nocomplain object o1} 1
@@ -48,7 +50,6 @@
   ? {c1 info has mixin ::M} 1  
   ? {c1 info has mixin ::M1} {expected class but got "::M1" for parameter class}
   #? {::nsf::parametercheck hasmixin,arg=::M c1} 1
-
   
   #? {::nsf::is type c1 C} 1
   ? {c1 info has type C} 1