diff --git a/swh/scheduler/backend.py b/swh/scheduler/backend.py
--- a/swh/scheduler/backend.py
+++ b/swh/scheduler/backend.py
@@ -99,7 +99,8 @@
         """
         keys = [key for key in self.task_type_keys if key in task_type]
         query = format_query(
-            """insert into task_type ({keys}) values ({placeholders})""",
+            """insert into task_type ({keys}) values ({placeholders})
+            on conflict do nothing""",
             keys)
         cur.execute(query, [task_type[key] for key in keys])
 
diff --git a/swh/scheduler/tests/test_scheduler.py b/swh/scheduler/tests/test_scheduler.py
--- a/swh/scheduler/tests/test_scheduler.py
+++ b/swh/scheduler/tests/test_scheduler.py
@@ -13,7 +13,6 @@
 
 from arrow import utcnow
 
-import psycopg2
 import pytest
 
 from .common import tasks_from_template, TEMPLATES, TASK_TYPES
@@ -38,15 +37,17 @@
         tt = TASK_TYPES['git']
         swh_scheduler.create_task_type(tt)
         assert tt == swh_scheduler.get_task_type(tt['type'])
-        with pytest.raises(psycopg2.IntegrityError,
-                           match=r'\(type\)=\(%s\)' % tt['type']):
-            swh_scheduler.create_task_type(tt)
-
         tt2 = TASK_TYPES['hg']
         swh_scheduler.create_task_type(tt2)
         assert tt == swh_scheduler.get_task_type(tt['type'])
         assert tt2 == swh_scheduler.get_task_type(tt2['type'])
 
+    def test_create_task_type_idempotence(self, swh_scheduler):
+        tt = TASK_TYPES['git']
+        swh_scheduler.create_task_type(tt)
+        swh_scheduler.create_task_type(tt)
+        assert tt == swh_scheduler.get_task_type(tt['type'])
+
     def test_get_task_types(self, swh_scheduler):
         tt, tt2 = TASK_TYPES['git'], TASK_TYPES['hg']
         swh_scheduler.create_task_type(tt)