diff --git a/lib/matrix_api/model/auth/authentication_data.dart b/lib/matrix_api/model/auth/authentication_data.dart
index 248ad27e..ad340400 100644
--- a/lib/matrix_api/model/auth/authentication_data.dart
+++ b/lib/matrix_api/model/auth/authentication_data.dart
@@ -29,8 +29,8 @@ class AuthenticationData {
 
   Map<String, dynamic> toJson() {
     final data = <String, dynamic>{};
-    data['type'] = type;
-    data['session'] = session;
+    if (type != null) data['type'] = type;
+    if (session != null) data['session'] = session;
     return data;
   }
 }