diff --git a/mail-server.nix b/mail-server.nix
index a4dd368..b1ccbc6 100644
--- a/mail-server.nix
+++ b/mail-server.nix
@@ -211,7 +211,7 @@ in {
       };
       groups.mail-server-solr = {
         gid = 8983;
-        members = "mail-server-solr";
+        members = [ "mail-server-solr" ];
       };
     };