diff --git a/lib/__init__.py b/lib/__init__.py
index cf8c06ae..fd13b5a2 100644
--- a/lib/__init__.py
+++ b/lib/__init__.py
@@ -59,7 +59,7 @@ from psycopg2._psycopg import NotSupportedError, OperationalError
 from psycopg2._psycopg import _connect, apilevel, threadsafety, paramstyle
 from psycopg2._psycopg import __version__
 
-from psycopg2 import tz
+from psycopg2 import tz, _py3
 
 
 # Register default adapters.
@@ -147,7 +147,7 @@ def connect(dsn=None,
     if port is not None:
         items.append(('port', port))
 
-    items.extend([(k, v) for (k, v) in kwargs.iteritems() if v is not None])
+    items.extend([(k, v) for (k, v) in _py3.iteritems(kwargs) if v is not None])
 
     if dsn is not None and items:
         raise TypeError(
diff --git a/lib/_py3.py b/lib/_py3.py
new file mode 100644
index 00000000..fd051144
--- /dev/null
+++ b/lib/_py3.py
@@ -0,0 +1,19 @@
+import sys
+
+PY3 = sys.version_info[0] == 3
+
+
+if PY3:
+    import _thread
+
+    def iteritems(d, **kw):
+        return iter(d.items(**kw))
+
+    thread = _thread
+else:
+    import thread as _thread
+
+    def iteritems(d, **kw):
+        return iter(d.iteritems(**kw))
+
+    thread = _thread
diff --git a/lib/errorcodes.py b/lib/errorcodes.py
index 12c300f6..5e67c876 100644
--- a/lib/errorcodes.py
+++ b/lib/errorcodes.py
@@ -29,6 +29,9 @@ This module contains symbolic names for all PostgreSQL error codes.
 #   http://www.postgresql.org/docs/current/static/errcodes-appendix.html
 #
 
+from psycopg2 import _py3
+
+
 def lookup(code, _cache={}):
     """Lookup an error code or class code and return its symbolic name.
 
@@ -38,7 +41,7 @@ def lookup(code, _cache={}):
         return _cache[code]
 
     # Generate the lookup map at first usage.
-    for k, v in globals().iteritems():
+    for k, v in _py3.iteritems(globals()):
         if isinstance(v, str) and len(v) in (2, 5):
             _cache[v] = k
 
diff --git a/lib/extras.py b/lib/extras.py
index 69de6147..4ab596f6 100644
--- a/lib/extras.py
+++ b/lib/extras.py
@@ -26,7 +26,6 @@ and classes until a better place in the distribution is found.
 # License for more details.
 
 import os as _os
-import sys as _sys
 import time as _time
 import re as _re
 
@@ -37,6 +36,7 @@ except:
 
 import psycopg2
 from psycopg2 import extensions as _ext
+from psycopg2 import _py3
 from psycopg2.extensions import cursor as _cursor
 from psycopg2.extensions import connection as _connection
 from psycopg2.extensions import adapt as _A
@@ -191,7 +191,7 @@ class DictRow(list):
         self._index = data[1]
 
     # drop the crusty Py2 methods
-    if _sys.version_info[0] > 2:
+    if _py3.PY3:
         items = iteritems; del iteritems
         keys = iterkeys; del iterkeys
         values = itervalues; del itervalues
@@ -788,7 +788,7 @@ def register_hstore(conn_or_curs, globally=False, unicode=False,
             array_oid = tuple([x for x in array_oid if x])
 
     # create and register the typecaster
-    if _sys.version_info[0] < 3 and unicode:
+    if not _py3.PY3 and unicode:
         cast = HstoreAdapter.parse_unicode
     else:
         cast = HstoreAdapter.parse
diff --git a/lib/pool.py b/lib/pool.py
index 4f858ab1..24e9ea8f 100644
--- a/lib/pool.py
+++ b/lib/pool.py
@@ -26,6 +26,7 @@ This module implements thread-safe (and not) connection pools.
 
 import psycopg2
 import psycopg2.extensions as _ext
+from psycopg2 import _py3
 
 
 class PoolError(psycopg2.Error):
@@ -204,8 +205,7 @@ class PersistentConnectionPool(AbstractConnectionPool):
 
         # we we'll need the thread module, to determine thread ids, so we
         # import it here and copy it in an instance variable
-        import thread
-        self.__thread = thread
+        self.__thread = _py3.thread
 
     def getconn(self):
         """Generate thread id and return a connection."""