Index: generic/nsf.c
===================================================================
diff -u -r7c55d2affeb04a210fd1a3668cfb2200f4b81aaf -ref60fd6efc8dc75cd58cffa54dacb5b62a22691d
--- generic/nsf.c	(.../nsf.c)	(revision 7c55d2affeb04a210fd1a3668cfb2200f4b81aaf)
+++ generic/nsf.c	(.../nsf.c)	(revision ef60fd6efc8dc75cd58cffa54dacb5b62a22691d)
@@ -28997,7 +28997,10 @@
     ParamDefsRefCountIncr(paramDefs);
     result = ArgumentParse(interp, (TCL_OBJC_T)objc, objv, NULL, NsfGlobalObjs[NSF_PARSE_ARGS],
                            paramDefs->paramsPtr, paramDefs->nrParams, paramDefs->serial,
-                           processFlags|NSF_ARGPARSE_START_ZERO|RUNTIME_STATE(interp)->doCheckArguments,
+                           processFlags
+                           |NSF_ARGPARSE_START_ZERO
+                           |NSF_ARGPARSE_FORCE_REQUIRED
+                           |RUNTIME_STATE(interp)->doCheckArguments,
                            &pc);
 
     if (result == TCL_OK) {