diff --git a/wa/framework/plugin.py b/wa/framework/plugin.py
index c9828839..bc7ab832 100644
--- a/wa/framework/plugin.py
+++ b/wa/framework/plugin.py
@@ -81,19 +81,10 @@ class AttributeCollection(object):
     __repr__ = __str__
 
     def _to_attrcls(self, p):
-        old_owner = getattr(p, "_owner", None)
-        if isinstance(p, basestring):
-            p = self._attrcls(p)
-        elif isinstance(p, tuple) or isinstance(p, list):
-            p = self._attrcls(*p)
-        elif isinstance(p, dict):
-            p = self._attrcls(**p)
-        elif not isinstance(p, self._attrcls):
-            raise ValueError('Invalid parameter value: {}'.format(p))
-        if (p.name in self._attrs and not p.override and
-                p.name != 'modules'):  # TODO: HACK due to "diamond dependecy" in workloads...
+        if not isinstance(p, self._attrcls):
+            raise ValueError('Invalid attribute value: {}; must be a {}'.format(p, self._attrcls))
+        if (p.name in self._attrs and not p.override):
             raise ValueError('Attribute {} has already been defined.'.format(p.name))
-        p._owner = old_owner
         return p
 
     def __iadd__(self, other):
@@ -269,7 +260,6 @@ class PluginMeta(type):
     to_propagate = [
         ('parameters', Parameter, AttributeCollection),
         ('artifacts', Artifact, AttributeCollection),
-        ('core_modules', str, ListCollection),
     ]
 
     virtual_methods = ['validate', 'initialize', 'finalize']
@@ -299,8 +289,10 @@ class PluginMeta(type):
             if prop_attr in attrs:
                 pattrs = attrs[prop_attr] or []
                 for pa in pattrs:
-                    if not isinstance(pa, basestring):
-                        pa._owner = clsname
+                    if not isinstance(pa, attr_cls):
+                        msg = 'Invalid value "{}" for attribute "{}"; must be a {}'
+                        raise ValueError(msg.format(pa, prop_attr, attr_cls))
+                    pa._owner = clsname
                 propagated += pattrs
                 should_propagate = True
             if should_propagate:
@@ -339,13 +331,7 @@ class Plugin(object):
 
     kind = None
     name = None
-    parameters = [
-        Parameter('modules', kind=list,
-                  description="""
-                  Lists the modules to be loaded by this plugin. A module is a 
-                  plug-in that further extends functionality of an plugin.
-                  """),
-    ]
+    parameters = []
     artifacts = []
     aliases = []
     core_modules = []
diff --git a/wa/tests/data/extensions/devices/test_device.py b/wa/tests/data/extensions/devices/test_device.py
index 2c4d51ad..e2c9d278 100644
--- a/wa/tests/data/extensions/devices/test_device.py
+++ b/wa/tests/data/extensions/devices/test_device.py
@@ -23,7 +23,6 @@ class TestDevice(Plugin):
     kind = 'device'
 
     def __init__(self, *args, **kwargs):
-        self.modules = []
         self.boot_called = 0
         self.push_file_called = 0
         self.pull_file_called = 0
diff --git a/wa/tests/test_plugin.py b/wa/tests/test_plugin.py
index f47f488a..a8bc5c24 100644
--- a/wa/tests/test_plugin.py
+++ b/wa/tests/test_plugin.py
@@ -44,15 +44,8 @@ class PluginLoaderTest(TestCase):
 
 
 
-class MyMeta(PluginMeta):
-
-    virtual_methods = ['validate', 'virtual1', 'virtual2']
-
-
 class MyBasePlugin(Plugin):
 
-    __metaclass__ = MyMeta
-
     name = 'base'
     kind = 'test'
 
@@ -166,43 +159,6 @@ class PluginMetaTest(TestCase):
                 7,
             ]
 
-    def test_virtual_methods(self):
-        acid = MyAcidPlugin()
-        acid.virtual1()
-        assert_equal(acid.v1, 1)
-        assert_equal(acid.vv1, 1)
-        assert_equal(acid.v2, 0)
-        assert_equal(acid.vv2, 0)
-        assert_equal(acid.v3, 'acid')
-        acid.virtual2()
-        acid.virtual2()
-        assert_equal(acid.v1, 1)
-        assert_equal(acid.vv1, 1)
-        assert_equal(acid.v2, 2)
-        assert_equal(acid.vv2, 2)
-
-    def test_initialization(self):
-        class MyExt(Plugin):
-            name = 'myext'
-            kind = 'test'
-            values = {'a': 0}
-            def __init__(self, *args, **kwargs):
-                super(MyExt, self).__init__(*args, **kwargs)
-                self.instance_init = 0
-            def initialize(self, context):
-                self.values['a'] += 1
-
-        class MyChildExt(MyExt):
-            name = 'mychildext'
-            def initialize(self, context):
-                self.instance_init += 1
-
-        ext = MyChildExt()
-        ext.initialize(None)
-
-        assert_equal(MyExt.values['a'], 1)
-        assert_equal(ext.instance_init, 1)
-
 
 class ParametersTest(TestCase):