diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
index ab42ed7..aa2b8bb 100644
--- a/Lib/test/test_signal.py
+++ b/Lib/test/test_signal.py
@@ -611,6 +611,15 @@
         # and the handler should have been called
         self.assertEqual(self.hndl_called, True)
 
+    def test_setitimer_tiny(self):
+        # bpo-30807: C setitimer() takes a microsecond-resolution interval.
+        # Check that float -> timeval conversion doesn't round
+        # the interval down to zero, which would disable the timer.
+        self.itimer = signal.ITIMER_REAL
+        signal.setitimer(self.itimer, 1e-6)
+        time.sleep(1)
+        self.assertEqual(self.hndl_called, True)
+
 
 class PendingSignalsTests(unittest.TestCase):
     """