diff -r bbfc65d05588 Lib/test/test_select.py
--- a/Lib/test/test_select.py	Thu Apr 07 10:48:29 2011 -0400
+++ b/Lib/test/test_select.py	Thu Apr 07 21:06:59 2011 +0200
@@ -20,6 +20,7 @@
         self.assertRaises(TypeError, select.select, [self.Nope()], [], [])
         self.assertRaises(TypeError, select.select, [self.Almost()], [], [])
         self.assertRaises(TypeError, select.select, [], [], [], "not a number")
+        self.assertRaises(ValueError, select.select, [], [], [], -1)
 
     def test_returned_list_identity(self):
         # See issue #8329
diff -r bbfc65d05588 Modules/selectmodule.c
--- a/Modules/selectmodule.c	Thu Apr 07 10:48:29 2011 -0400
+++ b/Modules/selectmodule.c	Thu Apr 07 21:06:59 2011 +0200
@@ -234,6 +234,11 @@
                             "timeout period too long");
             return NULL;
         }
+        if (timeout < 0) {
+            PyErr_SetString(PyExc_ValueError,
+                        "timeout must be non-negative");
+            return NULL;
+        }
         seconds = (long)timeout;
         timeout = timeout - (double)seconds;
         tv.tv_sec = seconds;