diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
index 9cb7481..8964b67 100644
--- a/Modules/selectmodule.c
+++ b/Modules/selectmodule.c
@@ -237,8 +237,12 @@
 #endif
         tv.tv_sec = (long)sec;
 #else
-        if (_PyTime_ObjectToTimeval(tout, &tv.tv_sec, &tv.tv_usec) == -1)
+        /* 64-bit OS X has struct timeval.tv_usec as an int (and thus still 4
+           bytes as required), but no longer defined by a long. */
+        long tv_usec = tv.tv_usec;
+        if (_PyTime_ObjectToTimeval(tout, &tv.tv_sec, &tv_usec) == -1)
             return NULL;
+        tv.tv_usec = tv_usec;
 #endif
         if (tv.tv_sec < 0) {
             PyErr_SetString(PyExc_ValueError, "timeout must be non-negative");