diff --git a/actions/matrixsynapse b/actions/matrixsynapse
index 659a31872..5d578498a 100755
--- a/actions/matrixsynapse
+++ b/actions/matrixsynapse
@@ -70,7 +70,7 @@ def subcommand_post_install(_):
         'attributes': {
             'uid': 'uid',
             'name': 'uid',
-            'mail': ''
+            'mail': None
         }
     }
     config['password_providers'][0]['config'] = ldap_config