diff --git a/cms/djangoapps/contentstore/tests/tests.py b/cms/djangoapps/contentstore/tests/tests.py
index a3e4548465..350ef47f17 100644
--- a/cms/djangoapps/contentstore/tests/tests.py
+++ b/cms/djangoapps/contentstore/tests/tests.py
@@ -319,6 +319,10 @@ class ForumTestCase(CourseTestCase):
         self.course.discussion_blackouts = [(t.isoformat(), t2.isoformat()) for t, t2 in times2]
         self.assertFalse(self.course.forum_posts_allowed)
 
+        # test if user gives empty blackout date it should return true for forum_posts_allowed
+        self.course.discussion_blackouts = [[]]
+        self.assertTrue(self.course.forum_posts_allowed)
+
 
 @ddt
 class CourseKeyVerificationTestCase(CourseTestCase):
diff --git a/common/lib/xmodule/xmodule/course_module.py b/common/lib/xmodule/xmodule/course_module.py
index cb91fe4b6b..405eb07980 100644
--- a/common/lib/xmodule/xmodule/course_module.py
+++ b/common/lib/xmodule/xmodule/course_module.py
@@ -1294,13 +1294,13 @@ class CourseDescriptor(CourseFields, SequenceDescriptor):
             blackout_periods = [(date_proxy.from_json(start),
                                  date_proxy.from_json(end))
                                 for start, end
-                                in self.discussion_blackouts]
+                                in filter(None, self.discussion_blackouts)]
             now = datetime.now(UTC())
             for start, end in blackout_periods:
                 if start <= now <= end:
                     return False
         except:
-            log.exception("Error parsing discussion_blackouts for course {0}".format(self.id))
+            log.exception("Error parsing discussion_blackouts %s for course %s", self.discussion_blackouts, self.id)
 
         return True