diff --git a/AUTHORS b/AUTHORS
index d8a07764a5..3e96b5759c 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -166,4 +166,5 @@ Nicholas Dupoux <njdupoux1994@gmail.com>
 John Eskew <jeskew@edx.org>
 Juanan Pereira <juanan.pereira@ehu.es>
 Clinton Blackburn <cblackburn@edx.org>
-Dennis Jen <djen@edx.org>
\ No newline at end of file
+Dennis Jen <djen@edx.org>
+Filippo Valsorda <hi@filippo.io>
diff --git a/common/lib/xmodule/xmodule/fields.py b/common/lib/xmodule/xmodule/fields.py
index 74d7a61b7d..a1b7496bf8 100644
--- a/common/lib/xmodule/xmodule/fields.py
+++ b/common/lib/xmodule/xmodule/fields.py
@@ -80,6 +80,8 @@ class Date(Field):
         else:
             raise TypeError("Cannot convert {!r} to json".format(value))
 
+    enforce_type = from_json
+
 TIMEDELTA_REGEX = re.compile(r'^((?P<days>\d+?) day(?:s?))?(\s)?((?P<hours>\d+?) hour(?:s?))?(\s)?((?P<minutes>\d+?) minute(?:s)?)?(\s)?((?P<seconds>\d+?) second(?:s)?)?$')
 
 
@@ -117,6 +119,15 @@ class Timedelta(Field):
                 values.append("%d %s" % (cur_value, attr))
         return ' '.join(values)
 
+    def enforce_type(self, value):
+        """
+        Ensure that when set explicitly the Field is set to a timedelta
+        """
+        if isinstance(value, datetime.timedelta) or value is None:
+            return value
+
+        return self.from_json(value)
+
 
 class RelativeTime(Field):
     """
@@ -219,3 +230,12 @@ class RelativeTime(Field):
         if len(stringified) == 7:
             stringified = '0' + stringified
         return stringified
+
+    def enforce_type(self, value):
+        """
+        Ensure that when set explicitly the Field is set to a timedelta
+        """
+        if isinstance(value, datetime.timedelta) or value is None:
+            return value
+
+        return self.from_json(value)
diff --git a/common/lib/xmodule/xmodule/tests/test_fields.py b/common/lib/xmodule/xmodule/tests/test_fields.py
index 47318ee4c5..d00d8f85c7 100644
--- a/common/lib/xmodule/xmodule/tests/test_fields.py
+++ b/common/lib/xmodule/xmodule/tests/test_fields.py
@@ -41,6 +41,19 @@ class DateTest(unittest.TestCase):
             DateTest.date.from_json("2013-01-01T00:00:00+01:00"),
             datetime.timedelta(hours=1, seconds=1))
 
+    def test_enforce_type(self):
+        self.assertEqual(DateTest.date.enforce_type(None), None)
+        self.assertEqual(DateTest.date.enforce_type(""), None)
+        self.assertEqual(DateTest.date.enforce_type("2012-12-31T23:00:01"),
+            datetime.datetime(2012, 12, 31, 23, 0, 1, tzinfo=UTC()))
+        self.assertEqual(DateTest.date.enforce_type(1234567890000),
+            datetime.datetime(2009, 2, 13, 23, 31, 30, tzinfo=UTC()))
+        self.assertEqual(DateTest.date.enforce_type(
+            datetime.datetime(2014, 5, 9, 21, 1, 27, tzinfo=UTC())),
+            datetime.datetime(2014, 5, 9, 21, 1, 27, tzinfo=UTC()))
+        with self.assertRaises(TypeError):
+            DateTest.date.enforce_type([1])
+
     def test_return_None(self):
         self.assertIsNone(DateTest.date.from_json(""))
         self.assertIsNone(DateTest.date.from_json(None))
@@ -102,6 +115,16 @@ class TimedeltaTest(unittest.TestCase):
             datetime.timedelta(days=1, seconds=46799)
         )
 
+    def test_enforce_type(self):
+        self.assertEqual(TimedeltaTest.delta.enforce_type(None), None)
+        self.assertEqual(TimedeltaTest.delta.enforce_type(
+            datetime.timedelta(days=1, seconds=46799)),
+            datetime.timedelta(days=1, seconds=46799))
+        self.assertEqual(TimedeltaTest.delta.enforce_type('1 day 46799 seconds'),
+            datetime.timedelta(days=1, seconds=46799))
+        with self.assertRaises(TypeError):
+            TimedeltaTest.delta.enforce_type([1])
+
     def test_to_json(self):
         self.assertEqual(
             '1 days 46799 seconds',
@@ -143,6 +166,16 @@ class RelativeTimeTest(unittest.TestCase):
         with self.assertRaises(ValueError):
             RelativeTimeTest.delta.from_json("77:77:77")
 
+    def test_enforce_type(self):
+        self.assertEqual(RelativeTimeTest.delta.enforce_type(None), None)
+        self.assertEqual(RelativeTimeTest.delta.enforce_type(
+            datetime.timedelta(days=1, seconds=46799)),
+            datetime.timedelta(days=1, seconds=46799))
+        self.assertEqual(RelativeTimeTest.delta.enforce_type('0:05:07'),
+            datetime.timedelta(seconds=307))
+        with self.assertRaises(TypeError):
+            RelativeTimeTest.delta.enforce_type([1])
+
     def test_to_json(self):
         self.assertEqual(
             "01:02:03",
diff --git a/requirements/edx/github.txt b/requirements/edx/github.txt
index b0c77e8018..a70b5cd04d 100644
--- a/requirements/edx/github.txt
+++ b/requirements/edx/github.txt
@@ -17,7 +17,7 @@
 -e git+https://github.com/appliedsec/pygeoip.git@95e69341cebf5a6a9fbf7c4f5439d458898bdc3b#egg=pygeoip
 
 # Our libraries:
--e git+https://github.com/edx/XBlock.git@aed7a2c51a59836e435259ad0fb41f8e865fa530#egg=XBlock
+-e git+https://github.com/edx/XBlock.git@f0e53538be7ce90584a03cc7dd3f06bd43e12ac2#egg=XBlock
 -e git+https://github.com/edx/codejail.git@71f5c5616e2a73ae8cecd1ff2362774a773d3665#egg=codejail
 -e git+https://github.com/edx/diff-cover.git@v0.5.0#egg=diff_cover
 -e git+https://github.com/edx/js-test-tool.git@v0.1.5#egg=js_test_tool