diff --git a/generic/nsf.h b/generic/nsf.h
index bf647fbb..6f0e4617 100644
--- a/generic/nsf.h
+++ b/generic/nsf.h
@@ -110,7 +110,7 @@
  * Support for TIP 627
  * https://core.tcl-lang.org/tips/doc/trunk/tip/627.md
 */
-# define TCL_OBJC_T           size_t
+# define TCL_OBJC_T           Tcl_Size
 # define TCL_OBJCMDPROC_T     Tcl_ObjCmdProc2
 # define TCL_CREATEOBJCOMMAND Tcl_CreateObjCommand2
 # define TCL_NRCREATECOMMAND  Tcl_NRCreateCommand2