Index: library/nx/nx.tcl
===================================================================
diff -u -r6a609930f16d6c18b3a938aecb2d2659c6a9bb8a -r643c9e05493cc12dcc72e1f48a5b6fa47ba8aa41
--- library/nx/nx.tcl	(.../nx.tcl)	(revision 6a609930f16d6c18b3a938aecb2d2659c6a9bb8a)
+++ library/nx/nx.tcl	(.../nx.tcl)	(revision 643c9e05493cc12dcc72e1f48a5b6fa47ba8aa41)
@@ -2260,7 +2260,7 @@
     }
 
     if {$parameterOptions ne "" && "substdefault" in [split $parameterOptions ,]} {
-      set defaultValue [subst $defaultValue]
+      set defaultValue [apply [list {} [list subst $defaultValue]]]
     }
 
     if {$initblock eq "" && !$configurable && !$incremental