diff --git a/nixos/modules/services/network-filesystems/openafs/server.nix b/nixos/modules/services/network-filesystems/openafs/server.nix
index d782f782165..4fce650b013 100644
--- a/nixos/modules/services/network-filesystems/openafs/server.nix
+++ b/nixos/modules/services/network-filesystems/openafs/server.nix
@@ -61,6 +61,7 @@ in {
       };
 
       advertisedAddresses = mkOption {
+        type = types.listOf types.str;
         default = [];
         description = "List of IP addresses this server is advertised under. See NetInfo(5)";
       };