diff --git a/cps/db.py b/cps/db.py
index fe89c50b..e35417dc 100644
--- a/cps/db.py
+++ b/cps/db.py
@@ -436,7 +436,7 @@ class CalibreDB():
         self.instances.add(self)
 
 
-    def initSession(self, expire_on_commit):
+    def initSession(self, expire_on_commit=True):
         self.session = self.session_factory()
         self.session.expire_on_commit = expire_on_commit
         self.update_title_sort(self.config)