Index: generic/gentclAPI.tcl
===================================================================
diff -u -r67f901aeccddd0ef42d927686e9eadb217cb1c8a -r24571ae44c492c681d3efd2f2d2f5169ad7d6d57
--- generic/gentclAPI.tcl	(.../gentclAPI.tcl)	(revision 67f901aeccddd0ef42d927686e9eadb217cb1c8a)
+++ generic/gentclAPI.tcl	(.../gentclAPI.tcl)	(revision 24571ae44c492c681d3efd2f2d2f5169ad7d6d57)
@@ -365,7 +365,7 @@
     if {[dict get $::definitions($key) clientData] ne ""} {
       set stubNN "NSF_nonnull(1) "
       set NN " NSF_nonnull(2)"
-      regsub \n\n $intro "\n\n  assert(clientData);\n" intro
+      regsub \n\n $intro "\n\n  assert(clientData != NULL);\n" intro
     } else {
       set stubNN ""
       set NN ""