diff --git a/odoo/api.py b/odoo/api.py
index 68b92943640..cf56718b032 100644
--- a/odoo/api.py
+++ b/odoo/api.py
@@ -452,6 +452,7 @@ class Environment(Mapping):
         self.cr, self.uid, self.context, self.su = self.args = args
         self.registry = Registry(cr.dbname)
         self.cache = envs.cache
+        self._cache_key = {}                    # memo {field: cache_key}
         self._protected = envs.protected        # proxy to shared data structure
         self.all = envs
         envs.add(self)
@@ -709,6 +710,36 @@ class Environment(Mapping):
         """ Delay recomputations (deprecated: this is not the default behavior). """
         yield
 
+    def cache_key(self, field):
+        """ Return the cache key corresponding to ``field.depends_context``. """
+        try:
+            return self._cache_key[field]
+
+        except KeyError:
+            def get(key, get_context=self.context.get):
+                if key == 'company':
+                    return self.company.id
+                elif key == 'uid':
+                    return (self.uid, self.su)
+                elif key == 'active_test':
+                    return get_context('active_test', field.context.get('active_test', True))
+                else:
+                    val = get_context(key)
+                    try:
+                        hash(val)
+                    except TypeError:
+                        raise TypeError(
+                            "Can only create cache keys from hashable values, "
+                            "got non-hashable value {!r} at context key {!r} "
+                            "(dependency of field {})".format(val, key, field)
+                        ) from None  # we don't need to chain the exception created 2 lines above
+                    else:
+                        return val
+
+            result = tuple(get(key) for key in field.depends_context)
+            self._cache_key[field] = result
+            return result
+
 
 class Environments(object):
     """ A common object for all environments in a request. """
@@ -742,7 +773,7 @@ class Cache(object):
     def contains(self, record, field):
         """ Return whether ``record`` has a value for ``field``. """
         if field.depends_context:
-            key = field.cache_key(record.env)
+            key = record.env.cache_key(field)
             return key in self._data.get(field, {}).get(record.id, {})
         return record.id in self._data.get(field, ())
 
@@ -751,7 +782,7 @@ class Cache(object):
         try:
             value = self._data[field][record._ids[0]]
             if field.depends_context:
-                value = value[field.cache_key(record.env)]
+                value = value[record.env.cache_key(field)]
             return value
         except KeyError:
             if default is NOTHING:
@@ -761,7 +792,7 @@ class Cache(object):
     def set(self, record, field, value):
         """ Set the value of ``field`` for ``record``. """
         if field.depends_context:
-            key = field.cache_key(record.env)
+            key = record.env.cache_key(field)
             self._data[field].setdefault(record._ids[0], {})[key] = value
         else:
             self._data[field][record._ids[0]] = value
@@ -769,7 +800,7 @@ class Cache(object):
     def update(self, records, field, values):
         """ Set the values of ``field`` for several ``records``. """
         if field.depends_context:
-            key = field.cache_key(records.env)
+            key = records.env.cache_key(field)
             field_cache = self._data[field]
             for record_id, value in zip(records._ids, values):
                 field_cache.setdefault(record_id, {})[key] = value
@@ -786,7 +817,7 @@ class Cache(object):
     def get_values(self, records, field):
         """ Return the cached values of ``field`` for ``records``. """
         field_cache = self._data[field]
-        key = field.cache_key(records.env) if field.depends_context else None
+        key = records.env.cache_key(field) if field.depends_context else None
         for record_id in records._ids:
             try:
                 if key is not None:
@@ -799,7 +830,7 @@ class Cache(object):
     def get_records_different_from(self, records, field, value):
         """ Return the subset of ``records`` that has not ``value`` for ``field``. """
         field_cache = self._data[field]
-        key = field.cache_key(records.env) if field.depends_context else None
+        key = records.env.cache_key(field) if field.depends_context else None
         ids = []
         for record_id in records._ids:
             try:
@@ -822,7 +853,7 @@ class Cache(object):
             values = self._data.get(field, {})
             if record.id not in values:
                 continue
-            if field.depends_context and field.cache_key(record.env) not in values[record.id]:
+            if field.depends_context and record.env.cache_key(field) not in values[record.id]:
                 continue
             yield field
 
diff --git a/odoo/fields.py b/odoo/fields.py
index 449544e2250..3982f9c00da 100644
--- a/odoo/fields.py
+++ b/odoo/fields.py
@@ -632,34 +632,6 @@ class Field(MetaField('DummyField', (object,), {})):
         Property = records.env['ir.property']
         return Property.search_multi(self.name, self.model_name, operator, value)
 
-    #
-    # Cache key for context-dependent fields
-    #
-
-    def cache_key(self, env):
-        """ Return the cache key corresponding to ``self.depends_context``. """
-
-        def get(key, get_context=env.context.get):
-            if key == 'company':
-                return env.company.id
-            elif key == 'uid':
-                return (env.uid, env.su)
-            elif key == 'active_test':
-                return get_context('active_test', self.context.get('active_test', True))
-            else:
-                v = get_context(key)
-                try: hash(v)
-                except TypeError:
-                    raise TypeError(
-                        "Can only create cache keys from hashable values, "
-                        "got non-hashable value {!r} at context key {!r} "
-                        "(dependency of field {})".format(v, key, self)
-                    ) from None # we don't need to chain the exception created 2 lines above
-                else:
-                    return v
-
-        return tuple(get(key) for key in self.depends_context)
-
     #
     # Setup of field triggers
     #