--- a/cubicweb/misc/migration/bootstrapmigration_repository.py	Wed Feb 17 14:03:56 2016 +0100
+++ b/cubicweb/misc/migration/bootstrapmigration_repository.py	Wed Feb 17 14:01:35 2016 +0100
@@ -45,6 +45,7 @@
         cursor.execute(dbh.sql_sequence_current_state('entities_id_seq'))
         lasteid = cursor.fetchone()[0]
     except: # programming error, already migrated
+        session.rollback()
         return
 
     cursor.execute(dbh.sql_drop_sequence('entities_id_seq'))