diff --git a/Misc/NEWS b/Misc/NEWS
index 32effc6660a..d421cbd56a0 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -54,6 +54,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #18909: Fix _tkinter.tkapp.interpaddr() on Windows 64-bit, don't cast
+  64-bit pointer to long (32 bits).
+
 - Issue #18876: The FileIO.mode attribute now better reflects the actual mode
   under which the file was opened.  Patch by Erik Bray.
 
diff --git a/Modules/_tkinter.c b/Modules/_tkinter.c
index 9a0db0e9ffa..bef7837e7e6 100644
--- a/Modules/_tkinter.c
+++ b/Modules/_tkinter.c
@@ -2462,7 +2462,7 @@ Tkapp_InterpAddr(PyObject *self, PyObject *args)
     if (!PyArg_ParseTuple(args, ":interpaddr"))
         return NULL;
 
-    return PyLong_FromLong((long)Tkapp_Interp(self));
+    return PyLong_FromVoidPtr(Tkapp_Interp(self));
 }
 
 static PyObject *