diff --git a/src/govoplan_addresses/backend/capabilities.py b/src/govoplan_addresses/backend/capabilities.py
index b61a835..4aa7ba2 100644
--- a/src/govoplan_addresses/backend/capabilities.py
+++ b/src/govoplan_addresses/backend/capabilities.py
@@ -1232,7 +1232,10 @@ def _address_book_contact_updated_at(session: Any, address_book_ids: list[str])
         if updated_at is None:
             continue
         key = str(address_book_id)
-        revisions[key] = max(revisions.get(key, updated_at), updated_at)
+        revisions[key] = max(
+            _aware_datetime(revisions.get(key, updated_at)),
+            _aware_datetime(updated_at),
+        )
     return revisions
 
 
@@ -1306,7 +1309,10 @@ def _address_list_updated_at(session: Any, address_list_ids: list[str]) -> dict[
         if updated_at is None:
             continue
         key = str(address_list_id)
-        revisions[key] = max(revisions.get(key, updated_at), updated_at)
+        revisions[key] = max(
+            _aware_datetime(revisions.get(key, updated_at)),
+            _aware_datetime(updated_at),
+        )
     return revisions
 
 
@@ -1314,14 +1320,14 @@ def _recipient_source_revision(book: AddressBook, latest_contact_updated_at: dat
     stamps: list[datetime] = [book.updated_at]
     if latest_contact_updated_at is not None:
         stamps.append(latest_contact_updated_at)
-    return max(stamps).isoformat()
+    return max(_aware_datetime(item) for item in stamps).isoformat()
 
 
 def _address_list_source_revision(address_list: AddressList, latest_entry_updated_at: datetime | None = None) -> str:
     stamps: list[datetime] = [address_list.updated_at]
     if latest_entry_updated_at is not None:
         stamps.append(latest_entry_updated_at)
-    return max(stamps).isoformat()
+    return max(_aware_datetime(item) for item in stamps).isoformat()
 
 
 def _channel_facts_contact_id(source: DistributionSourceReference) -> str:
diff --git a/tests/test_addresses_service.py b/tests/test_addresses_service.py
index 9d144b2..c6be140 100644
--- a/tests/test_addresses_service.py
+++ b/tests/test_addresses_service.py
@@ -1208,7 +1208,9 @@ END:VCARD
                 contact_postal_address_id=contact.postal_addresses[0].id,
             ),
         )
-        self.session.commit()
+        # Providers must also work before the surrounding transaction commits;
+        # SQLite aggregate timestamps are naive while new ORM rows are UTC-aware.
+        self.session.flush()
 
         capability = AddressesContactPointResolutionCapability()
         direct = capability.resolve_contact_points(