diff --git a/backend/app/dav/caldav.py b/backend/app/dav/caldav.py
index 1a62dd6..cc92f01 100644
--- a/backend/app/dav/caldav.py
+++ b/backend/app/dav/caldav.py
@@ -52,7 +52,7 @@ def _qn(prefix: str, local: str) -> str:
 def _xml_response(root: ET.Element, status: int = 207) -> Response:
     body = b'<?xml version="1.0" encoding="utf-8"?>\n' + ET.tostring(root, encoding='utf-8')
     headers = {
-        'DAV': '1, 2, 3, calendar-access',
+        'DAV': '1, 2, 3, calendar-access, addressbook',
         'Content-Type': 'application/xml; charset=utf-8',
     }
     return Response(body, status=status, headers=headers)
@@ -88,7 +88,7 @@ def basic_auth(f):
 # ---------------------------------------------------------------------------
 
 DAV_HEADERS = {
-    'DAV': '1, 2, 3, calendar-access',
+    'DAV': '1, 2, 3, calendar-access, addressbook',
 }
 
 ALLOW_COLLECTION = 'OPTIONS, PROPFIND, REPORT, DELETE, MKCALENDAR'