Index: generic/nsf.c
===================================================================
diff -u -rc1ac4a3f2987f5ff235083261800bcb85cc4463f -r2d3e0da7e6a7d8f9811ad22598fde7ede516e010
--- generic/nsf.c	(.../nsf.c)	(revision c1ac4a3f2987f5ff235083261800bcb85cc4463f)
+++ generic/nsf.c	(.../nsf.c)	(revision 2d3e0da7e6a7d8f9811ad22598fde7ede516e010)
@@ -14355,7 +14355,9 @@
       int length;
 
       tailMethodObj = objv[1];
-      if (Tcl_ListObjLength(interp, objv[1], &length) == TCL_OK) {
+      if ((((object->flags & NSF_KEEP_CALLER_SELF) != 0u) ||
+           ((object->flags & NSF_PER_OBJECT_DISPATCH) != 0u)) &&
+          Tcl_ListObjLength(interp, objv[1], &length) == TCL_OK) {
         if (length > 1) {
           Tcl_ListObjIndex(interp, objv[1], length - 1, &tailMethodObj);
         }