Index: library/nx/nx.tcl
===================================================================
diff -u -r764405083cfd6152d6956674e54f3a77cf7e1dcd -r6a3cd1a111aa693839ec3d788262ce18be74bf91
--- library/nx/nx.tcl	(.../nx.tcl)	(revision 764405083cfd6152d6956674e54f3a77cf7e1dcd)
+++ library/nx/nx.tcl	(.../nx.tcl)	(revision 6a3cd1a111aa693839ec3d788262ce18be74bf91)
@@ -1560,6 +1560,9 @@
       # In case the "assign method" has changed, forward variable
       # setting in configure (e.g. called during initialization of
       # object parameters) to the slot.
+      if {${:accessor} == 0} {
+	error "parameter ${:name}: option 'noaccessor' cannot be used together with required accessor (assign method)" 
+      }
       lappend options slot=[::nsf::self] invokesetter
     }
     if {[info exists :arg]} {lappend options arg=${:arg}}