diff --git a/cloudkitty/rating/hash/db/sqlalchemy/alembic/versions/c88a06b1cfce_clean_hashmap_fields_constraints.py b/cloudkitty/rating/hash/db/sqlalchemy/alembic/versions/c88a06b1cfce_clean_hashmap_fields_constraints.py
new file mode 100644
index 00000000..48cc2d9c
--- /dev/null
+++ b/cloudkitty/rating/hash/db/sqlalchemy/alembic/versions/c88a06b1cfce_clean_hashmap_fields_constraints.py
@@ -0,0 +1,62 @@
+"""Clean hashmap fields constraints.
+
+Revision ID: c88a06b1cfce
+Revises: f8c799db4aa0
+Create Date: 2016-05-19 18:06:43.315066
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'c88a06b1cfce'
+down_revision = 'f8c799db4aa0'
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+    with op.batch_alter_table(
+        'hashmap_fields',
+        # NOTE(sheeprine): Forced reflection is needed because of SQLAlchemy's
+        # SQLite backend limitation reflecting ON DELETE clauses.
+        reflect_args=[
+            sa.Column(
+                'service_id',
+                sa.Integer,
+                sa.ForeignKey(
+                    'hashmap_services.id',
+                    ondelete='CASCADE',
+                    name='fk_hashmap_fields_service_id_hashmap_services'),
+                nullable=False)]) as batch_op:
+        batch_op.drop_constraint(
+            u'uniq_field',
+            type_='unique')
+        batch_op.create_unique_constraint(
+            'uniq_field_per_service',
+            ['service_id', 'name'])
+        batch_op.drop_constraint(
+            'uniq_map_service_field',
+            type_='unique')
+
+
+def downgrade():
+    with op.batch_alter_table(
+        'hashmap_fields',
+        reflect_args=[
+            sa.Column(
+                'service_id',
+                sa.Integer,
+                sa.ForeignKey(
+                    'hashmap_services.id',
+                    ondelete='CASCADE',
+                    name='fk_hashmap_fields_service_id_hashmap_services'),
+                nullable=False)]) as batch_op:
+        batch_op.create_unique_constraint(
+            u'uniq_field',
+            ['field_id', 'name'])
+        batch_op.create_unique_constraint(
+            'uniq_map_service_field',
+            ['service_id', 'name'])
+        batch_op.drop_constraint(
+            'uniq_field_per_service',
+            type_='unique')
diff --git a/cloudkitty/rating/hash/db/sqlalchemy/models.py b/cloudkitty/rating/hash/db/sqlalchemy/models.py
index ae3fe601..36033de1 100644
--- a/cloudkitty/rating/hash/db/sqlalchemy/models.py
+++ b/cloudkitty/rating/hash/db/sqlalchemy/models.py
@@ -117,14 +117,10 @@ class HashMapField(Base, HashMapBase):
     @declarative.declared_attr
     def __table_args__(cls):
         args = (
-            schema.UniqueConstraint(
-                'field_id',
-                'name',
-                name='uniq_field'),
             schema.UniqueConstraint(
                 'service_id',
                 'name',
-                name='uniq_map_service_field'),
+                name='uniq_field_per_service'),
             HashMapBase.__table_args__,)
         return args