diff --git a/ligo/gracedb/rest.py b/ligo/gracedb/rest.py
index b88e9f2b5d7d16aff9b5950adac25bc8b73dd823..4f07a1b974b503871cbdbbb3923d2bb40b7acef0 100644
--- a/ligo/gracedb/rest.py
+++ b/ligo/gracedb/rest.py
@@ -1157,7 +1157,7 @@ class GraceDb(GsiRest):
         return self.get(uri).json()['numRows']
 
     def createSuperevent(self, t_start, t_0, t_end, preferred_event,
-                         category='production', events=[], labels=None):
+                         category='production', events=None, labels=None):
         """Create a superevent.
 
         All LIGO-Virgo users can create test superevents, but special
@@ -1201,28 +1201,40 @@ class GraceDb(GsiRest):
         if labels:
             if isinstance(labels, six.string_types):
                 labels = [labels]
-            elif isinstance(labels, list):
-                pass
+            elif isinstance(labels, (list, tuple)):
+                # Validate each entry
+                if any([not isinstance(l, six.string_types) for l in labels]):
+                    err_msg = "One of the provided labels is not a string"
+                    raise TypeError(err_msg)
             else:
                 raise TypeError("labels arg is {0}, should be str or list"
                                 .format(type(labels)))
             # Check labels against those in database
             for l in labels:
                 if l not in self.allowed_labels:
-                    raise NameError(("Label '{0}' does not exist in the "
-                                    "database").format(l))
+                    raise ValueError(("Label '{0}' does not exist in the "
+                                     "database").format(l))
         if events:
             if isinstance(events, six.string_types):
                 events = [events]
-            elif isinstance(events, list):
-                pass
+            elif isinstance(events, (list, tuple)):
+                if any([not isinstance(e, six.string_types) for e in events]):
+                    err_msg = \
+                        "One of the provided event graceids is not a string"
+                    raise TypeError(err_msg)
             else:
                 raise TypeError("events arg is {0}, should be str or list"
                                 .format(type(events)))
 
-        # validate category, convert to short form if necessary
-        category = self._getCode(category.lower(),
-                                 self.superevent_categories)
+        # Validate category, convert to short form if necessary
+        if not isinstance(category, six.string_types):
+            err_msg = "category arg is {0}, should be a string".format(
+                type(category))
+            raise TypeError(err_msg)
+        category = self._getCode(category, self.superevent_categories)
+        # Note: category can be None here as a result of processing
+        # by _getCode, which indicates failure to match the provided
+        # superevent category
         if not category:
             raise ValueError("category must be one of: {0}".format(
                 list(six.itervalues(self.superevent_categories))))