Index: library/nx/nx.tcl
===================================================================
diff -u -rbb1a4116720d5f205e44ec71f03857a340751fc3 -rcb4ee10b48bd3ab85d67d9f60617f6090a8adf59
--- library/nx/nx.tcl	(.../nx.tcl)	(revision bb1a4116720d5f205e44ec71f03857a340751fc3)
+++ library/nx/nx.tcl	(.../nx.tcl)	(revision cb4ee10b48bd3ab85d67d9f60617f6090a8adf59)
@@ -2273,6 +2273,13 @@
     ::nsf::var::unset -nocomplain=$nocomplain $obj $prop
   }
 
+  ::nx::VariableSlot public method value=exists {obj prop} {
+    if {[string match "__*" [namespace tail [self]]]} {
+      set prop "__private(${:domain},$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}]"