--- a/testing/marionette/client/marionette_driver/wait.py
+++ b/testing/marionette/client/marionette_driver/wait.py
@@ -24,18 +24,18 @@ class Wait(object):
     condition, as well as the frequency with which to check the
     condition.  Furthermore, the user may configure the wait to ignore
     specific types of exceptions whilst waiting, such as
     `errors.NoSuchElementException` when searching for an element on
     the page.
 
     """
 
-    def __init__(self, marionette, timeout=DEFAULT_TIMEOUT,
-                 interval=DEFAULT_INTERVAL, ignored_exceptions=None,
+    def __init__(self, marionette, timeout=None,
+                 interval=None, ignored_exceptions=None,
                  clock=None):
         """Configure the Wait instance to have a custom timeout, interval, and
         list of ignored exceptions.  Optionally a different time
         implementation than the one provided by the standard library
         (time) can also be provided.
 
         Sample usage::
 
@@ -66,20 +66,20 @@ class Wait(object):
 
         :param clock: Allows overriding the use of the runtime's
             default time library.  See `wait.SystemClock` for
             implementation details.
 
         """
 
         self.marionette = marionette
-        self.timeout = timeout
+        self.timeout = timeout if timeout is not None else DEFAULT_TIMEOUT
+        self.interval = interval if interval is not None else DEFAULT_INTERVAL
         self.clock = clock or SystemClock()
         self.end = self.clock.now + self.timeout
-        self.interval = interval
 
         exceptions = []
         if ignored_exceptions is not None:
             if isinstance(ignored_exceptions, collections.Iterable):
                 exceptions.extend(iter(ignored_exceptions))
             else:
                 exceptions.append(ignored_exceptions)
         self.exceptions = tuple(set(exceptions))