diff --git a/src/sakia/data/processors/identities.py b/src/sakia/data/processors/identities.py
index 8252252894408a979639eeb7c169a938e0c5d84a..414385605f25db4f7f6cd955f41713bf3e4b2edf 100644
--- a/src/sakia/data/processors/identities.py
+++ b/src/sakia/data/processors/identities.py
@@ -136,7 +136,7 @@ class IdentitiesProcessor:
                and memberships_data['uid'] == identity.uid:
                 identity.written = True
                 for ms in memberships_data['memberships']:
-                    if ms['written'] > identity.membership_written_on:
+                    if ms['written'] and ms['written'] > identity.membership_written_on:
                         identity.membership_buid = BlockUID(ms['blockNumber'], ms['blockHash'])
                         identity.membership_type = ms['membership']