Index: generic/nsf.c
===================================================================
diff -u -N -r172a32e2cc8e38216bdf9995e2e72bd2044c9f15 -r94a8ea7c8b50082b0b6e34e4713669dd77caa7b5
--- generic/nsf.c	(.../nsf.c)	(revision 172a32e2cc8e38216bdf9995e2e72bd2044c9f15)
+++ generic/nsf.c	(.../nsf.c)	(revision 94a8ea7c8b50082b0b6e34e4713669dd77caa7b5)
@@ -24505,6 +24505,7 @@
       if (argumentObj->typePtr == &NsfFlagObjType
           && flagPtr->signature == paramPtr
           && flagPtr->serial == serial
+          && flagPtr->paramPtr != NULL /* when the parameter was previously used in a cget */
           ) {
         /*
          * The argument was processed before and the Tcl_Obj is still valid.