diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 504e2cbd140..7661a00056a 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -387,7 +387,7 @@ buffered_clear(buffered *self)
 /* Because this can call arbitrary code, it shouldn't be called when
    the refcount is 0 (that is, not directly from tp_dealloc unless
    the refcount has been temporarily re-incremented). */
-PyObject *
+static PyObject *
 buffered_dealloc_warn(buffered *self, PyObject *source)
 {
     if (self->ok && self->raw) {