diff --git a/reclass/datatypes/parameters.py b/reclass/datatypes/parameters.py
index f40b259..e40ded1 100644
--- a/reclass/datatypes/parameters.py
+++ b/reclass/datatypes/parameters.py
@@ -25,37 +25,12 @@
 
 from collections import namedtuple
 from reclass.utils.dictpath import DictPath
+from reclass.utils.parameterdict import ParameterDict
+from reclass.utils.parameterlist import ParameterList
 from reclass.values.value import Value
 from reclass.values.valuelist import ValueList
 from reclass.errors import InfiniteRecursionError, ResolveError, ResolveErrorList, InterpolationError, BadReferencesError
 
-class ParameterDict(dict):
-    def __init__(self, *args, **kwargs):
-        self._uri = kwargs.pop('uri', None)
-        dict.__init__(self, *args, **kwargs)
-
-    @property
-    def uri(self):
-        return self._uri
-
-    @uri.setter
-    def uri(self, uri):
-        self._uri = uri
-
-
-class ParameterList(list):
-    def __init__(self, *args, **kwargs):
-        self._uri = kwargs.pop('uri', None)
-        list.__init__(self, *args, **kwargs)
-
-    @property
-    def uri(self):
-        return self._uri
-
-    @uri.setter
-    def uri(self, uri):
-        self._uri = uri
-
 
 class Parameters(object):
     '''
@@ -83,8 +58,8 @@
 
     def __init__(self, mapping, settings, uri, parse_strings=True):
         self._settings = settings
-        self._base = {}
         self._uri = uri
+        self._base = ParameterDict(uri=self._uri)
         self._unrendered = None
         self._escapes_handled = {}
         self._inv_queries = []
@@ -215,6 +190,7 @@
             else:
                 value = self._merge_recurse(cur.get(key), value)
             cur[key] = value
+        cur.uri = new.uri
         return cur
 
     def _merge_recurse(self, cur, new):
diff --git a/reclass/datatypes/tests/test_parameters.py b/reclass/datatypes/tests/test_parameters.py
index 2fcc899..013bd88 100644
--- a/reclass/datatypes/tests/test_parameters.py
+++ b/reclass/datatypes/tests/test_parameters.py
@@ -17,6 +17,7 @@
 
 from reclass.settings import Settings
 from reclass.datatypes import Parameters
+from reclass.utils.parameterdict import ParameterDict
 from reclass.values.value import Value
 from reclass.values.scaitem import ScaItem
 from reclass.errors import ChangedFixedError, InfiniteRecursionError, InterpolationError, ResolveError, ResolveErrorList, TypeMergeError
@@ -46,7 +47,7 @@
     def _construct_mocked_params(self, iterable=None, settings=SETTINGS):
         p = Parameters(iterable, settings, '')
         self._base = base = p._base
-        p._base = mock.MagicMock(spec_set=dict, wraps=base)
+        p._base = mock.MagicMock(spec_set=ParameterDict, wraps=base)
         p._base.__repr__ = mock.MagicMock(autospec=dict.__repr__,
                                           return_value=repr(base))
         p._base.__getitem__.side_effect = base.__getitem__
@@ -291,6 +292,16 @@
         p1.interpolate()
         self.assertEqual(p1.as_dict()['key'], None)
 
+    def test_merge_list_over_dict(self):
+        p1 = Parameters({}, SETTINGS, '')
+        p2 = Parameters({'one': { 'a': { 'b': 'c' } } }, SETTINGS, 'second')
+        p3 = Parameters({'one': { 'a': [ 'b' ] } }, SETTINGS, 'third')
+        with self.assertRaises(TypeMergeError) as e:
+            p1.merge(p2)
+            p1.merge(p3)
+            p1.interpolate()
+        self.assertEqual(e.exception.message, "-> \n   Canot merge list over dictionary, at one:a, in second; third")
+
     # def test_merge_bare_dict_over_dict(self):
         # settings = Settings({'allow_bare_override': True})
         # p1 = Parameters(dict(key=SIMPLE), settings, '')
diff --git a/reclass/utils/parameterdict.py b/reclass/utils/parameterdict.py
new file mode 100644
index 0000000..6319a0b
--- /dev/null
+++ b/reclass/utils/parameterdict.py
@@ -0,0 +1,12 @@
+class ParameterDict(dict):
+    def __init__(self, *args, **kwargs):
+        self._uri = kwargs.pop('uri', None)
+        dict.__init__(self, *args, **kwargs)
+
+    @property
+    def uri(self):
+        return self._uri
+
+    @uri.setter
+    def uri(self, uri):
+        self._uri = uri
diff --git a/reclass/utils/parameterlist.py b/reclass/utils/parameterlist.py
new file mode 100644
index 0000000..f2473df
--- /dev/null
+++ b/reclass/utils/parameterlist.py
@@ -0,0 +1,12 @@
+class ParameterList(list):
+    def __init__(self, *args, **kwargs):
+        self._uri = kwargs.pop('uri', None)
+        list.__init__(self, *args, **kwargs)
+
+    @property
+    def uri(self):
+        return self._uri
+
+    @uri.setter
+    def uri(self, uri):
+        self._uri = uri