diff --git a/gssapi/__init__.py b/gssapi/__init__.py
index cb89f73..73aa9df 100644
--- a/gssapi/__init__.py
+++ b/gssapi/__init__.py
@@ -38,3 +38,17 @@
 from gssapi.mechs import Mechanism  # noqa
 
 from gssapi._utils import set_encoding  # noqa
+
+__all__ = [
+    'AddressType',
+    'Credentials',
+    'IntEnumFlagSet',
+    'Mechanism',
+    'MechType',
+    'Name',
+    'NameType',
+    'OID',
+    'RequirementFlag',
+    'SecurityContext',
+    'set_encoding',
+]