diff --git a/Lib/unittest/signals.py b/Lib/unittest/signals.py
index e6a5fc5..251b488 100644
--- a/Lib/unittest/signals.py
+++ b/Lib/unittest/signals.py
@@ -35,8 +35,13 @@ class _InterruptHandler(object):
         if self.called:
             self.default_handler(signum, frame)
         self.called = True
+        stopped = False
         for result in _results.keys():
             result.stop()
+            stopped = True
+        if not stopped:
+            # if there aren't any registered results, delegate immediately
+            self.default_handler(signum, frame)
 
 _results = weakref.WeakKeyDictionary()
 def registerResult(result):