diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
index 2261bb854cb765..f8db5d5723fb28 100644
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -654,7 +654,7 @@ def test_create_tmp(self, repetitions=10):
             hostname = hostname.replace(':', r'\072')
         pid = os.getpid()
         pattern = re.compile(r"(?P<time>\d+)\.M(?P<M>\d{1,6})P(?P<P>\d+)"
-                             r"Q(?P<Q>\d+)\.(?P<host>[^:/]+)")
+                             r"Q(?P<Q>\d+)\.(?P<host>[^:/]*)")
         previous_groups = None
         for x in xrange(repetitions):
             tmp_file = self._box._create_tmp()