diff --git a/Include/internal/pycore_long.h b/Include/internal/pycore_long.h
index 1d1a3c9467a090..8bead00e70640c 100644
--- a/Include/internal/pycore_long.h
+++ b/Include/internal/pycore_long.h
@@ -55,8 +55,7 @@ extern void _PyLong_FiniTypes(PyInterpreterState *interp);
 
 /* other API */
 
-void
-_PyLong_ExactDealloc(PyObject *self);
+PyAPI_FUNC(void) _PyLong_ExactDealloc(PyObject *self);
 
 #define _PyLong_SMALL_INTS _Py_SINGLETON(small_ints)