diff --git a/GPy/core/parameterization/index_operations.py b/GPy/core/parameterization/index_operations.py
index 3d6ce64d..e4803f37 100644
--- a/GPy/core/parameterization/index_operations.py
+++ b/GPy/core/parameterization/index_operations.py
@@ -79,7 +79,7 @@ class ParameterIndexOperations(object):
         return self._properties.keys()
 
     def iterproperties(self):
-        return self._properties.iterkeys()
+        return iter(self._properties)
 
     def shift_right(self, start, size):
         for ind in self.iterindices():