diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 23ba3df866b..29e000bde4a 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -297,7 +297,7 @@ _enter_buffered_busy(buffered *self)
          * Note that non-daemon threads have already exited here, so this
          * shouldn't affect carefully written threaded I/O code.
          */
-        st = PyThread_acquire_lock_timed(self->lock, 1e6, 0);
+        st = PyThread_acquire_lock_timed(self->lock, (PY_TIMEOUT_T)1e6, 0);
     }
     Py_END_ALLOW_THREADS
     if (relax_locking && st != PY_LOCK_ACQUIRED) {