Index: generic/nsf.c
===================================================================
diff -u -re4500c77b2bdbb0733a1503d765be84f15509be3 -rdb831678bc92ce4e39bf4ff303f32491a3c4f9d9
--- generic/nsf.c	(.../nsf.c)	(revision e4500c77b2bdbb0733a1503d765be84f15509be3)
+++ generic/nsf.c	(.../nsf.c)	(revision db831678bc92ce4e39bf4ff303f32491a3c4f9d9)
@@ -13087,13 +13087,14 @@
   assert(outObjPtr); // autoadded
 
   if (unlikely(pPtr->converterArg != NULL)) {
-    Tcl_Obj *objv[3];
+    Tcl_Obj *objv[4];
     /*fprintf(stderr, "ConvertToTclobj %s (must be %s)\n", ObjStr(objPtr), ObjStr(pPtr->converterArg));*/
 
     objv[1] = pPtr->converterArg;
-    objv[2] = objPtr;
+    objv[2] = NsfGlobalObjs[NSF_OPTION_STRICT];
+    objv[3] = objPtr;
 
-    result = NsfCallCommand(interp, NSF_IS, 3, objv);
+    result = NsfCallCommand(interp, NSF_STRING_IS, 4, objv);
     if (likely(result == TCL_OK)) {
       int success;
       Tcl_GetIntFromObj(interp, Tcl_GetObjResult(interp), &success);
Index: generic/nsfInt.h
===================================================================
diff -u -r92ab630ebd3c1b907e3d0fdf97cc07914245c028 -rdb831678bc92ce4e39bf4ff303f32491a3c4f9d9
--- generic/nsfInt.h	(.../nsfInt.h)	(revision 92ab630ebd3c1b907e3d0fdf97cc07914245c028)
+++ generic/nsfInt.h	(.../nsfInt.h)	(revision db831678bc92ce4e39bf4ff303f32491a3c4f9d9)
@@ -637,11 +637,11 @@
   /* constants */
   NSF_ALIAS, NSF_ARGS, NSF_CMD, NSF_FILTER, NSF_FORWARD, 
   NSF_METHOD,  NSF_OBJECT, NSF_SETTER, NSF_SETTERNAME, NSF_VALUECHECK,
-  NSF_GUARD_OPTION, NSF___UNKNOWN__, NSF_ARRAY, NSF_GET, NSF_SET,
+  NSF_GUARD_OPTION, NSF___UNKNOWN__, NSF_ARRAY, NSF_GET, NSF_SET, NSF_OPTION_STRICT,
   NSF_OBJECT_UNKNOWN_HANDLER, NSF_ARGUMENT_UNKNOWN_HANDLER,
   /* Partly redefined Tcl commands; leave them together at the end */
   NSF_EXPR, NSF_FORMAT, NSF_INFO_BODY, NSF_INFO_FRAME, NSF_INTERP, 
-  NSF_IS, NSF_EVAL,
+  NSF_STRING_IS, NSF_EVAL,
   NSF_RENAME
 } NsfGlobalNames;
 #if !defined(NSF_C)
@@ -660,7 +660,7 @@
   /* constants */
   "alias", "args", "cmd", "filter",  "forward", 
   "method", "object", "setter", "settername", "valuecheck",
-  "-guard", "__unknown__", "::array", "get", "set",
+  "-guard", "__unknown__", "::array", "get", "set", "-strict",
   /* nsf tcl commands */
   "::nsf::object::unknown",
   "::nsf::argument::unknown",
Index: generic/nsfShadow.c
===================================================================
diff -u -r92ab630ebd3c1b907e3d0fdf97cc07914245c028 -rdb831678bc92ce4e39bf4ff303f32491a3c4f9d9
--- generic/nsfShadow.c	(.../nsfShadow.c)	(revision 92ab630ebd3c1b907e3d0fdf97cc07914245c028)
+++ generic/nsfShadow.c	(.../nsfShadow.c)	(revision db831678bc92ce4e39bf4ff303f32491a3c4f9d9)
@@ -406,7 +406,7 @@
 #endif
     rc |= NsfReplaceCommand(interp, NSF_FORMAT,     NULL, initialized);
     rc |= NsfReplaceCommand(interp, NSF_INTERP,     NULL, initialized);
-    rc |= NsfReplaceCommand(interp, NSF_IS,         NULL, initialized);
+    rc |= NsfReplaceCommand(interp, NSF_STRING_IS,  NULL, initialized);
 
     /* for the following commands, we have to add our own semantics */
     rc |= NsfReplaceCommand(interp, NSF_INFO_BODY,  Nsf_InfoBodyObjCmd, initialized);