Index: library/nx/nx.tcl
===================================================================
diff -u -N -r77a193c118f4ae2b0ccd0913e39326e4f0f53fe6 -rfc11b2380eef48346410636908936e9468c74807
--- library/nx/nx.tcl	(.../nx.tcl)	(revision 77a193c118f4ae2b0ccd0913e39326e4f0f53fe6)
+++ library/nx/nx.tcl	(.../nx.tcl)	(revision fc11b2380eef48346410636908936e9468c74807)
@@ -2273,6 +2273,10 @@
     ::nsf::var::unset -nocomplain=$nocomplain $obj $prop
   }
 
+  ::nx::VariableSlot public method value=exists {obj prop} {
+    ::nsf::var::exists $obj $prop
+  }
+
   ::nx::VariableSlot public method value=add {obj prop value {pos 0}} {
     if {![:isMultivalued]} {
       #puts stderr "... vars [[self] info vars] // [[self] eval {set :multiplicity}]"