diff --git a/Python/errors.c b/Python/errors.c
index 43d89bd..7b71051 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -664,7 +664,7 @@
 
 #undef PyErr_Warn
 
-int
+PyAPI_FUNC(int)
 PyErr_Warn(PyObject *category, char *message)
 {
 	return PyErr_WarnEx(category, message, 1);