diff --git a/GPy/core/parameterization/param.py b/GPy/core/parameterization/param.py
index a8408bf4..950314dd 100644
--- a/GPy/core/parameterization/param.py
+++ b/GPy/core/parameterization/param.py
@@ -4,7 +4,7 @@
 import itertools
 import numpy
 from parameter_core import Constrainable, adjust_name_for_printing
-from array_core import ObservableArray
+from array_core import ObservableArray, ParamList
 
 ###### printing
 __constraints_name__ = "Constraint"
diff --git a/GPy/core/parameterization/parameter_core.py b/GPy/core/parameterization/parameter_core.py
index 8bb33d6f..0bb97388 100644
--- a/GPy/core/parameterization/parameter_core.py
+++ b/GPy/core/parameterization/parameter_core.py
@@ -49,20 +49,19 @@ class Pickleable(object):
 
 class Parentable(object):
     def __init__(self, direct_parent=None, parent_index=None):
-        super(Parentable,self).__init__()        
+        super(Parentable,self).__init__()
         self._direct_parent_ = direct_parent
         self._parent_index_ = parent_index
-        self._highest_parent_ = highest_parent
 
     def has_parent(self):
         return self._direct_parent_ is not None
-    
+
     @property
     def _highest_parent_(self):
         if self._direct_parent_ is None:
             return self
         return self._direct_parent_._highest_parent_
-    
+
 class Nameable(Parentable):
     _name = None
     def __init__(self, name, direct_parent=None, parent_index=None):
@@ -101,8 +100,6 @@ class Constrainable(Nameable):
         """
         self._highest_parent_._unfix(self)
     unfix = unconstrain_fixed
-
-
     #===========================================================================
     # Constrain operations -> done
     #===========================================================================