1 files changed, 4 insertions, 0 deletions
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
index 5a6b13466c..fe69cd58dc 100644
--- a/Modules/selectmodule.c
+++ b/Modules/selectmodule.c
@@ -335,6 +335,10 @@ select_select_impl(PyObject *module, PyObject *rlist, PyObject *wlist,
         if (tvp) {
             timeout = deadline - _PyTime_GetMonotonicClock();
             if (timeout < 0) {
+                /* bpo-35310: lists were unmodified -- clear them explicitly */
+                FD_ZERO(&ifdset);
+                FD_ZERO(&ofdset);
+                FD_ZERO(&efdset);
                 n = 0;
                 break;
             }