diff --git a/openerp/api.py b/openerp/api.py
index 5c8b93892b7..6c70910633f 100644
--- a/openerp/api.py
+++ b/openerp/api.py
@@ -756,7 +756,7 @@ class Environment(object):
         """
         if not spec:
             return
-        for env in list(self.all):
+        for env in list(iter(self.all)):
             c = env.cache
             for field, ids in spec:
                 if ids is None:
@@ -769,7 +769,7 @@ class Environment(object):
 
     def invalidate_all(self):
         """ Clear the cache of all environments. """
-        for env in list(self.all):
+        for env in list(iter(self.all)):
             env.cache.clear()
             env.prefetch.clear()
             env.computed.clear()
diff --git a/openerp/models.py b/openerp/models.py
index 6e095049dd2..a93965c071a 100644
--- a/openerp/models.py
+++ b/openerp/models.py
@@ -5402,7 +5402,7 @@ class BaseModel(object):
         """ If `field` must be recomputed on some record in `self`, return the
             corresponding records that must be recomputed.
         """
-        for env in [self.env] + list(self.env.all):
+        for env in [self.env] + list(iter(self.env.all)):
             if env.todo.get(field) and env.todo[field] & self:
                 return env.todo[field]
 
@@ -5424,7 +5424,7 @@ class BaseModel(object):
         """ Recompute stored function fields. The fields and records to
             recompute have been determined by method :meth:`modified`.
         """
-        for env in list(self.env.all):
+        for env in list(iter(self.env.all)):
             while env.todo:
                 field, recs = next(env.todo.iteritems())
                 # evaluate the fields to recompute, and save them to database