diff --git a/slixmpp/features/feature_mechanisms/stanza/challenge.py b/slixmpp/features/feature_mechanisms/stanza/challenge.py
index 21a061ee..7fa76e18 100644
--- a/slixmpp/features/feature_mechanisms/stanza/challenge.py
+++ b/slixmpp/features/feature_mechanisms/stanza/challenge.py
@@ -19,7 +19,7 @@ class Challenge(StanzaBase):
 
     name = 'challenge'
     namespace = 'urn:ietf:params:xml:ns:xmpp-sasl'
-    interfaces = set(('value',))
+    interfaces = {'value'}
     plugin_attrib = name
 
     def setup(self, xml):
diff --git a/slixmpp/features/feature_mechanisms/stanza/failure.py b/slixmpp/features/feature_mechanisms/stanza/failure.py
index cc0ac877..29f0a343 100644
--- a/slixmpp/features/feature_mechanisms/stanza/failure.py
+++ b/slixmpp/features/feature_mechanisms/stanza/failure.py
@@ -18,7 +18,7 @@ class Failure(StanzaBase):
     namespace = 'urn:ietf:params:xml:ns:xmpp-sasl'
     interfaces = set(('condition', 'text'))
     plugin_attrib = name
-    sub_interfaces = set(('text',))
+    sub_interfaces = {'text'}
     conditions = set(('aborted', 'account-disabled', 'credentials-expired',
         'encryption-required', 'incorrect-encoding', 'invalid-authzid',
         'invalid-mechanism', 'malformed-request', 'mechansism-too-weak',
diff --git a/slixmpp/features/feature_mechanisms/stanza/response.py b/slixmpp/features/feature_mechanisms/stanza/response.py
index 8da236ba..b25a0592 100644
--- a/slixmpp/features/feature_mechanisms/stanza/response.py
+++ b/slixmpp/features/feature_mechanisms/stanza/response.py
@@ -19,7 +19,7 @@ class Response(StanzaBase):
 
     name = 'response'
     namespace = 'urn:ietf:params:xml:ns:xmpp-sasl'
-    interfaces = set(('value',))
+    interfaces = {'value'}
     plugin_attrib = name
 
     def setup(self, xml):
diff --git a/slixmpp/features/feature_starttls/stanza.py b/slixmpp/features/feature_starttls/stanza.py
index df50897e..ba58d93e 100644
--- a/slixmpp/features/feature_starttls/stanza.py
+++ b/slixmpp/features/feature_starttls/stanza.py
@@ -16,7 +16,7 @@ class STARTTLS(ElementBase):
 
     name = 'starttls'
     namespace = 'urn:ietf:params:xml:ns:xmpp-tls'
-    interfaces = set(('required',))
+    interfaces = {'required'}
     plugin_attrib = name
 
     def get_required(self):
diff --git a/slixmpp/plugins/xep_0004/stanza/field.py b/slixmpp/plugins/xep_0004/stanza/field.py
index 42f1210b..2bcc823a 100644
--- a/slixmpp/plugins/xep_0004/stanza/field.py
+++ b/slixmpp/plugins/xep_0004/stanza/field.py
@@ -16,7 +16,7 @@ class FormField(ElementBase):
     plugin_multi_attrib = 'fields'
     interfaces = set(('answer', 'desc', 'required', 'value',
                       'label', 'type', 'var'))
-    sub_interfaces = set(('desc',))
+    sub_interfaces = {'desc'}
     plugin_tag_map = {}
     plugin_attrib_map = {}
 
@@ -165,7 +165,7 @@ class FieldOption(ElementBase):
     name = 'option'
     plugin_attrib = 'option'
     interfaces = set(('label', 'value'))
-    sub_interfaces = set(('value',))
+    sub_interfaces = {'value'}
     plugin_multi_attrib = 'options'
 
 
diff --git a/slixmpp/plugins/xep_0004/stanza/form.py b/slixmpp/plugins/xep_0004/stanza/form.py
index 32bfc0e3..52b18f81 100644
--- a/slixmpp/plugins/xep_0004/stanza/form.py
+++ b/slixmpp/plugins/xep_0004/stanza/form.py
@@ -24,7 +24,7 @@ class Form(ElementBase):
     name = 'x'
     plugin_attrib = 'form'
     interfaces = OrderedSet(('instructions', 'reported', 'title', 'type', 'items', ))
-    sub_interfaces = set(('title',))
+    sub_interfaces = {'title'}
     form_types = set(('cancel', 'form', 'result', 'submit'))
 
     def __init__(self, *args, **kwargs):
diff --git a/slixmpp/plugins/xep_0030/stanza/info.py b/slixmpp/plugins/xep_0030/stanza/info.py
index 614b68de..a09c85a8 100644
--- a/slixmpp/plugins/xep_0030/stanza/info.py
+++ b/slixmpp/plugins/xep_0030/stanza/info.py
@@ -72,7 +72,7 @@ class DiscoInfo(ElementBase):
     namespace = 'http://jabber.org/protocol/disco#info'
     plugin_attrib = 'disco_info'
     interfaces = set(('node', 'features', 'identities'))
-    lang_interfaces = set(('identities',))
+    lang_interfaces = {'identities'}
 
     # Cache identities and features
     _identities = set()
diff --git a/slixmpp/plugins/xep_0060/stanza/base.py b/slixmpp/plugins/xep_0060/stanza/base.py
index b8f3d6cc..2f781e98 100644
--- a/slixmpp/plugins/xep_0060/stanza/base.py
+++ b/slixmpp/plugins/xep_0060/stanza/base.py
@@ -11,7 +11,7 @@ from slixmpp.xmlstream import ET
 
 class OptionalSetting(object):
 
-    interfaces = set(('required',))
+    interfaces = {'required'}
 
     def set_required(self, value):
         if value in (True, 'true', 'True', '1'):
diff --git a/slixmpp/plugins/xep_0060/stanza/pubsub.py b/slixmpp/plugins/xep_0060/stanza/pubsub.py
index 3f6f2719..841e69d2 100644
--- a/slixmpp/plugins/xep_0060/stanza/pubsub.py
+++ b/slixmpp/plugins/xep_0060/stanza/pubsub.py
@@ -23,7 +23,7 @@ class Affiliations(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'affiliations'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class Affiliation(ElementBase):
@@ -56,14 +56,14 @@ class Subscriptions(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'subscriptions'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class SubscribeOptions(ElementBase, OptionalSetting):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'subscribe-options'
     plugin_attrib = 'suboptions'
-    interfaces = set(('required',))
+    interfaces = {'required'}
 
 
 class Item(ElementBase):
@@ -105,7 +105,7 @@ class Create(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'create'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class Default(ElementBase):
@@ -125,7 +125,7 @@ class Publish(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'publish'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class Retract(ElementBase):
@@ -227,7 +227,7 @@ class PublishOptions(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'publish-options'
     plugin_attrib = 'publish_options'
-    interfaces = set(('publish_options',))
+    interfaces = {'publish_options'}
     is_extension = True
 
     def get_publish_options(self):
diff --git a/slixmpp/plugins/xep_0060/stanza/pubsub_event.py b/slixmpp/plugins/xep_0060/stanza/pubsub_event.py
index 1ba97c75..b2b53d3d 100644
--- a/slixmpp/plugins/xep_0060/stanza/pubsub_event.py
+++ b/slixmpp/plugins/xep_0060/stanza/pubsub_event.py
@@ -44,49 +44,49 @@ class EventRetract(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'retract'
     plugin_attrib = name
-    interfaces = set(('id',))
+    interfaces = {'id'}
 
 
 class EventItems(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'items'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class EventCollection(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'collection'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class EventAssociate(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'associate'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class EventDisassociate(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'disassociate'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class EventConfiguration(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'configuration'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class EventPurge(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'purge'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class EventDelete(ElementBase):
diff --git a/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py b/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py
index 402e5e30..bcb96149 100644
--- a/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py
+++ b/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py
@@ -41,7 +41,7 @@ class DefaultConfig(ElementBase):
 
 class OwnerAffiliations(Affiliations):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
     def append(self, affiliation):
         if not isinstance(affiliation, OwnerAffiliation):
@@ -58,26 +58,26 @@ class OwnerConfigure(Configure):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
     name = 'configure'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class OwnerDefault(OwnerConfigure):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class OwnerDelete(ElementBase, OptionalSetting):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
     name = 'delete'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class OwnerPurge(ElementBase, OptionalSetting):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
     name = 'purge'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
 
 class OwnerRedirect(ElementBase):
@@ -97,7 +97,7 @@ class OwnerSubscriptions(Subscriptions):
     name = 'subscriptions'
     namespace = 'http://jabber.org/protocol/pubsub#owner'
     plugin_attrib = name
-    interfaces = set(('node',))
+    interfaces = {'node'}
 
     def append(self, subscription):
         if not isinstance(subscription, OwnerSubscription):
diff --git a/slixmpp/plugins/xep_0085/stanza.py b/slixmpp/plugins/xep_0085/stanza.py
index de1bc645..f5048f45 100644
--- a/slixmpp/plugins/xep_0085/stanza.py
+++ b/slixmpp/plugins/xep_0085/stanza.py
@@ -37,7 +37,7 @@ class ChatState(ElementBase):
     name = ''
     namespace = 'http://jabber.org/protocol/chatstates'
     plugin_attrib = 'chat_state'
-    interfaces = set(('chat_state',))
+    interfaces = {'chat_state'}
     sub_interfaces = interfaces
     is_extension = True
 
diff --git a/slixmpp/plugins/xep_0086/stanza.py b/slixmpp/plugins/xep_0086/stanza.py
index cbc9429d..a28abafa 100644
--- a/slixmpp/plugins/xep_0086/stanza.py
+++ b/slixmpp/plugins/xep_0086/stanza.py
@@ -44,7 +44,7 @@ class LegacyError(ElementBase):
     name = 'legacy'
     namespace = Error.namespace
     plugin_attrib = name
-    interfaces = set(('condition',))
+    interfaces = {'condition'}
     overrides = ['set_condition']
 
     error_map = {'bad-request': ('modify', '400'),
diff --git a/slixmpp/plugins/xep_0138.py b/slixmpp/plugins/xep_0138.py
index 049060cf..ced81478 100644
--- a/slixmpp/plugins/xep_0138.py
+++ b/slixmpp/plugins/xep_0138.py
@@ -22,7 +22,7 @@ log = logging.getLogger(__name__)
 class Compression(ElementBase):
     name = 'compression'
     namespace = 'http://jabber.org/features/compress'
-    interfaces = set(('methods',))
+    interfaces = {'methods'}
     plugin_attrib = 'compression'
     plugin_tag_map = {}
     plugin_attrib_map = {}
@@ -37,7 +37,7 @@ class Compression(ElementBase):
 class Compress(StanzaBase):
     name = 'compress'
     namespace = 'http://jabber.org/protocol/compress'
-    interfaces = set(('method',))
+    interfaces = {'method'}
     sub_interfaces = interfaces
     plugin_attrib = 'compress'
     plugin_tag_map = {}
diff --git a/slixmpp/plugins/xep_0172/stanza.py b/slixmpp/plugins/xep_0172/stanza.py
index 305f3a00..c85137ab 100644
--- a/slixmpp/plugins/xep_0172/stanza.py
+++ b/slixmpp/plugins/xep_0172/stanza.py
@@ -46,7 +46,7 @@ class UserNick(ElementBase):
     namespace = 'http://jabber.org/protocol/nick'
     name = 'nick'
     plugin_attrib = name
-    interfaces = set(('nick',))
+    interfaces = {'nick'}
 
     def set_nick(self, nick):
         """
diff --git a/slixmpp/plugins/xep_0184/stanza.py b/slixmpp/plugins/xep_0184/stanza.py
index 03a0ff9c..1116eef9 100644
--- a/slixmpp/plugins/xep_0184/stanza.py
+++ b/slixmpp/plugins/xep_0184/stanza.py
@@ -13,7 +13,7 @@ class Request(ElementBase):
     namespace = 'urn:xmpp:receipts'
     name = 'request'
     plugin_attrib = 'request_receipt'
-    interfaces = set(('request_receipt',))
+    interfaces = {'request_receipt'}
     sub_interfaces = interfaces
     is_extension = True
 
diff --git a/slixmpp/plugins/xep_0224/stanza.py b/slixmpp/plugins/xep_0224/stanza.py
index 2b77dadd..d50d74b4 100644
--- a/slixmpp/plugins/xep_0224/stanza.py
+++ b/slixmpp/plugins/xep_0224/stanza.py
@@ -17,7 +17,7 @@ class Attention(ElementBase):
     name = 'attention'
     namespace = 'urn:xmpp:attention:0'
     plugin_attrib = 'attention'
-    interfaces = set(('attention',))
+    interfaces = {'attention'}
     is_extension = True
 
     def setup(self, xml):
diff --git a/slixmpp/stanza/error.py b/slixmpp/stanza/error.py
index 67f736c0..1499c652 100644
--- a/slixmpp/stanza/error.py
+++ b/slixmpp/stanza/error.py
@@ -53,7 +53,7 @@ class Error(ElementBase):
     plugin_attrib = 'error'
     interfaces = set(('code', 'condition', 'text', 'type',
                       'gone', 'redirect', 'by'))
-    sub_interfaces = set(('text',))
+    sub_interfaces = {'text'}
     plugin_attrib_map = {}
     plugin_tag_map = {}
     conditions = set(('bad-request', 'conflict', 'feature-not-implemented',
diff --git a/slixmpp/xmlstream/stanzabase.py b/slixmpp/xmlstream/stanzabase.py
index e7ffddc8..306fdb2e 100644
--- a/slixmpp/xmlstream/stanzabase.py
+++ b/slixmpp/xmlstream/stanzabase.py
@@ -213,7 +213,7 @@ class ElementBase(object):
         ...     name = "message"
         ...     namespace = "jabber:client"
         ...     interfaces = set(('to', 'from', 'type', 'body'))
-        ...     sub_interfaces = set(('body',))
+        ...     sub_interfaces = {'body'}
 
     The resulting Message stanza's contents may be accessed as so::
 
diff --git a/tests/test_stanza_element.py b/tests/test_stanza_element.py
index 240203cc..7b6c5561 100644
--- a/tests/test_stanza_element.py
+++ b/tests/test_stanza_element.py
@@ -140,7 +140,7 @@ class TestElementBase(SlixTest):
             name = "foo"
             namespace = "foo"
             interfaces = set(('bar', 'baz', 'qux'))
-            sub_interfaces = set(('baz',))
+            sub_interfaces = {'baz'}
 
             def get_qux(self):
               return 'qux'
@@ -149,7 +149,7 @@ class TestElementBase(SlixTest):
             name = "foobar"
             namespace = "foo"
             plugin_attrib = "foobar"
-            interfaces = set(('fizz',))
+            interfaces = {'fizz'}
 
         register_stanza_plugin(TestStanza, TestStanza, iterable=True)
         register_stanza_plugin(TestStanza, TestStanzaPlugin)
@@ -186,7 +186,7 @@ class TestElementBase(SlixTest):
             name = "foo"
             namespace = "foo"
             interfaces = set(('bar', 'baz', 'qux'))
-            sub_interfaces = set(('baz',))
+            sub_interfaces = {'baz'}
 
             def set_qux(self, value):
                 pass
@@ -195,7 +195,7 @@ class TestElementBase(SlixTest):
             name = "foobar"
             namespace = "foo"
             plugin_attrib = "foobar"
-            interfaces = set(('foobar',))
+            interfaces = {'foobar'}
 
         register_stanza_plugin(TestStanza, TestStanzaPlugin)
 
@@ -220,7 +220,7 @@ class TestElementBase(SlixTest):
             name = "foo"
             namespace = "foo"
             interfaces = set(('bar', 'baz', 'qux'))
-            sub_interfaces = set(('bar',))
+            sub_interfaces = {'bar'}
 
             def del_qux(self):
                 pass
@@ -229,7 +229,7 @@ class TestElementBase(SlixTest):
             name = "foobar"
             namespace = "foo"
             plugin_attrib = "foobar"
-            interfaces = set(('foobar',))
+            interfaces = {'foobar'}
 
         register_stanza_plugin(TestStanza, TestStanzaPlugin)
 
@@ -298,7 +298,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar',))
+            interfaces = {'bar'}
 
             def set_bar(self, value):
                 wrapper = ET.Element("{foo}wrapper")
@@ -458,13 +458,13 @@ class TestElementBase(SlixTest):
         class TestSubStanza(ElementBase):
             name = "sub"
             namespace = "baz"
-            interfaces = set(('attrib',))
+            interfaces = {'attrib'}
 
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
             interfaces = set(('bar','baz', 'qux'))
-            sub_interfaces = set(('qux',))
+            sub_interfaces = {'qux'}
 
             def set_qux(self, value):
                 self._set_sub_text('qux', text=value)
@@ -475,7 +475,7 @@ class TestElementBase(SlixTest):
         class TestStanzaPlugin(ElementBase):
             name = "plugin"
             namespace = "http://test/slash/bar"
-            interfaces = set(('attrib',))
+            interfaces = {'attrib'}
 
         register_stanza_plugin(TestStanza, TestSubStanza, iterable=True)
         register_stanza_plugin(TestStanza, TestStanzaPlugin)
@@ -592,7 +592,7 @@ class TestElementBase(SlixTest):
         class TestSubStanza(ElementBase):
             name = "foobar"
             namespace = "foo"
-            interfaces = set(('qux',))
+            interfaces = {'qux'}
 
         class TestStanza(ElementBase):
             name = "foo"
@@ -678,7 +678,7 @@ class TestElementBase(SlixTest):
             name = 'extended'
             namespace = 'foo'
             plugin_attrib = name
-            interfaces = set((name,))
+            interfaces = {name}
             is_extension = True
 
             def set_extended(self, value):
@@ -721,7 +721,7 @@ class TestElementBase(SlixTest):
             name = 'overrider'
             namespace = 'foo'
             plugin_attrib = name
-            interfaces = set(('bar',))
+            interfaces = {'bar'}
             overrides = ['set_bar']
 
             def setup(self, xml):