diff --git a/ipalib/plugable.py b/ipalib/plugable.py
index 803490908..70743f5a2 100644
--- a/ipalib/plugable.py
+++ b/ipalib/plugable.py
@@ -289,9 +289,15 @@ class Registrar(object):
 
 
 class API(ReadOnly):
-	def __init__(self, registrar):
+	def __init__(self, *allowed):
+		object.__setattr__(self, 'register', Registrar(*allowed))
 		object.__setattr__(self, '_API__plugins', [])
-		for (base, plugins) in registrar:
+
+	def __call__(self):
+		"""
+		Finalize the registration, instantiate the plugins.
+		"""
+		for (base, plugins) in self.register:
 			ns = NameSpace(self.__plugin_iter(base, plugins))
 			assert not hasattr(self, base.__name__)
 			object.__setattr__(self, base.__name__, ns)
diff --git a/ipalib/tests/test_plugable.py b/ipalib/tests/test_plugable.py
index 27841e2e2..2e87ea2c0 100644
--- a/ipalib/tests/test_plugable.py
+++ b/ipalib/tests/test_plugable.py
@@ -334,7 +334,10 @@ def test_API():
 		def method(self, n):
 			return n + 1
 
-	r = plugable.Registrar(base0, base1)
+	api = plugable.API(base0, base1)
+	r = api.register
+	assert isinstance(r, plugable.Registrar)
+	assert read_only(api, 'register') is r
 
 	class base0_plugin0(base0):
 		pass
@@ -360,10 +363,8 @@ def test_API():
 		pass
 	r(base1_plugin2)
 
-	registrants = tuple(r)
-
 	# Test API instance:
-	api = plugable.API(r)
+	api() # Calling instance performs finalization
 
 	def get_base(b):
 		return 'base%d' % b