diff --git a/ckanext/dcat/harvesters/_json.py b/ckanext/dcat/harvesters/_json.py
index 5eea7ac0..c058bc54 100644
--- a/ckanext/dcat/harvesters/_json.py
+++ b/ckanext/dcat/harvesters/_json.py
@@ -6,6 +6,7 @@
 import uuid
 
 import requests
+import sqlalchemy as sa
 
 from ckan import model
 from ckan import logic
@@ -273,7 +274,8 @@ def import_stage(self, harvest_object):
                 # the harvest object id (on the after_show hook from the harvester
                 # plugin)
                 model.Session.execute(
-                    'SET CONSTRAINTS harvest_object_package_id_fkey DEFERRED')
+                    sa.text('SET CONSTRAINTS harvest_object_package_id_fkey DEFERRED')
+                )
                 model.Session.flush()
 
             elif status == 'change':
diff --git a/ckanext/dcat/harvesters/rdf.py b/ckanext/dcat/harvesters/rdf.py
index 564ba1af..7bc402e3 100644
--- a/ckanext/dcat/harvesters/rdf.py
+++ b/ckanext/dcat/harvesters/rdf.py
@@ -6,6 +6,8 @@
 import hashlib
 import traceback
 
+import sqlalchemy as sa
+
 import ckan.plugins as p
 import ckan.model as model
 
@@ -278,7 +280,7 @@ def import_stage(self, harvest_object):
                                                                     harvest_object.guid))
             except p.toolkit.ObjectNotFound:
                 log.info('Package {0} already deleted.'.format(harvest_object.package_id))
-            
+
             return True
 
         if harvest_object.content is None:
@@ -392,7 +394,9 @@ def import_stage(self, harvest_object):
                         # Defer constraints and flush so the dataset can be indexed with
                         # the harvest object id (on the after_show hook from the harvester
                         # plugin)
-                        model.Session.execute('SET CONSTRAINTS harvest_object_package_id_fkey DEFERRED')
+                        model.Session.execute(
+                            sa.text('SET CONSTRAINTS harvest_object_package_id_fkey DEFERRED')
+                        )
                         model.Session.flush()
 
                         p.toolkit.get_action('package_create')(context, dataset)