diff --git a/accountant/api/views/models.py b/accountant/api/views/models.py
index ad6f8d1..81f3946 100644
--- a/accountant/api/views/models.py
+++ b/accountant/api/views/models.py
@@ -14,6 +14,8 @@
     You should have received a copy of the GNU Affero General Public License
     along with Accountant.  If not, see <http://www.gnu.org/licenses/>.
 """
+from copy import deepcopy
+
 from flask.ext.restful import fields
 
 # Account model.
@@ -54,7 +56,7 @@ ohlc_model = {
 }
 
 # Operation with sold model.
-operation_with_sold_model = {
+operation_model = {
     'id': fields.Integer(default=None),
     'operation_date': fields.DateTime(dt_format='iso8601'),
     'label': fields.String,
@@ -63,11 +65,13 @@ operation_with_sold_model = {
     'category': fields.String,
     'account_id': fields.Integer,
     'scheduled_operation_id': fields.Integer(default=None),
-    'sold': fields.Float,
     'confirmed': fields.Boolean,
     'canceled': fields.Boolean,
 }
 
+operation_with_sold_model = deepcopy(operation_model)
+operation_with_sold_model['sold'] = fields.Float
+
 # Scheduled operation model.
 scheduled_operation_model = {
     'id': fields.Integer,