diff --git a/fuel_external_git/handlers.py b/fuel_external_git/handlers.py
index 7e7363b..dd2c9cd 100644
--- a/fuel_external_git/handlers.py
+++ b/fuel_external_git/handlers.py
@@ -217,9 +217,12 @@ class ChangesWhitelistRuleCollectionHandler(CollectionHandler):
         :http: * 200 (OK)
                * 404 (dashboard entry not found in db)
         """
+        env_id = int(env_id)
         self.get_object_or_404(objects.Cluster, env_id)
         rules = self.collection.get_by_env_id(env_id)
-        return self.collection.to_list(rules)
+        if rules:
+            rules = self.collection.to_list(rules)
+        return rules
 
     @handle_errors
     @serialize
@@ -230,12 +233,27 @@ class ChangesWhitelistRuleCollectionHandler(CollectionHandler):
                * 400 (invalid object data specified)
                * 409 (object with such parameters already exists)
         """
+        env_id = int(env_id)
         data = self.checked_data(
             validate_method=self.validator.validate_one_or_multiple
         )
         for item in data:
             item['env_id'] = env_id
 
+        rules = self.collection.get_by_env_id(env_id)
+        existing_rules = []
+        if rules:
+            rules = self.collection.to_list(rules)
+            existing_rules = filter(
+                lambda i: len(filter(lambda o:
+                                     i['fuel_task'] == o['fuel_task'] and
+                                     i['rule'] == o['rule'],
+                                     rules)) > 0,
+                data
+            )
+        if existing_rules:
+            raise self.http(409, existing_rules)
+
         new_objs = []
         try:
             for item in data:
diff --git a/fuel_external_git/migrations/versions/954d4c3a76be_add_unique_constaint_to_whitelist_rule_.py b/fuel_external_git/migrations/versions/954d4c3a76be_add_unique_constaint_to_whitelist_rule_.py
new file mode 100644
index 0000000..13f46c5
--- /dev/null
+++ b/fuel_external_git/migrations/versions/954d4c3a76be_add_unique_constaint_to_whitelist_rule_.py
@@ -0,0 +1,39 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+"""add unique constaint to whitelist rule-task-env
+
+Revision ID: 954d4c3a76be
+Revises: fc4f164a7b6c
+Create Date: 2016-11-15 10:36:06.950577
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '954d4c3a76be'
+down_revision = 'fc4f164a7b6c'
+branch_labels = None
+depends_on = None
+
+from alembic import context
+from alembic import op
+
+
+def upgrade():
+    table_prefix = context.config.get_main_option('table_prefix')
+    op.create_unique_constraint('_env_id_rule_task_unique',
+                                table_prefix + 'changes_whitelist',
+                                ['env_id', 'rule', 'fuel_task'])
+
+
+def downgrade():
+    pass
diff --git a/fuel_external_git/objects.py b/fuel_external_git/objects.py
index 29da258..447bb42 100644
--- a/fuel_external_git/objects.py
+++ b/fuel_external_git/objects.py
@@ -220,9 +220,6 @@ class ChangesWhitelistRuleCollection(NailgunCollection):
 
     @classmethod
     def get_by_env_id(self, env_id):
-        whitelist = set()
-        for rule in ChangesWhitelistRuleCollection.all():
-            if env_id == rule.env_id:
-                whitelist.add(rule)
-
+        whitelist = filter(lambda r: r.env_id == env_id,
+                           ChangesWhitelistRuleCollection.all())
         return whitelist