diff --git a/common/djangoapps/util/converters.py b/common/djangoapps/util/converters.py
index 900371a0dd..ec2d29ecfa 100644
--- a/common/djangoapps/util/converters.py
+++ b/common/djangoapps/util/converters.py
@@ -18,10 +18,13 @@ def jsdate_to_time(field):
     """
     if field is None:
         return field
-    elif isinstance(field, basestring):  # iso format but ignores time zone assuming it's Z
-        d = datetime.datetime(*map(int, re.split('[^\d]', field)[:6]))   # stop after seconds. Debatable
+    elif isinstance(field, basestring):
+        # ISO format but ignores time zone assuming it's Z.
+        d = datetime.datetime(*map(int, re.split('[^\d]', field)[:6]))  # stop after seconds. Debatable
         return d.utctimetuple()
-    elif isinstance(field, int) or isinstance(field, float):
+    elif isinstance(field, (int, long, float)):
         return time.gmtime(field / 1000)
     elif isinstance(field, time.struct_time):
         return field
+    else:
+        raise ValueError("Couldn't convert %r to time" % field)