Index: generic/nsf.c
===================================================================
diff -u -r8cec7f90a2d5e046562c37c85c934137c4155860 -r4d1efbac0cfc34dc7f0bfcb13749182050db26a6
--- generic/nsf.c	(.../nsf.c)	(revision 8cec7f90a2d5e046562c37c85c934137c4155860)
+++ generic/nsf.c	(.../nsf.c)	(revision 4d1efbac0cfc34dc7f0bfcb13749182050db26a6)
@@ -10151,8 +10151,10 @@
     int i, found = -1;
 
     if (paramPtr->converter) {
+      Tcl_Obj *obj = Tcl_NewStringObj(option,optionLength);
       NsfPrintError(interp, "Parameter option '%s' unknown for parameter type '%s'",
-		    option, paramPtr->type);
+		    ObjStr(obj), paramPtr->type);
+      DECR_REF_COUNT(obj);
       return TCL_ERROR;
     }