diff --git a/nixos/modules/services/misc/matrix-synapse.nix b/nixos/modules/services/misc/matrix-synapse.nix
index dff58745304..d623e97b8b1 100644
--- a/nixos/modules/services/misc/matrix-synapse.nix
+++ b/nixos/modules/services/misc/matrix-synapse.nix
@@ -231,7 +231,7 @@ in {
         type = types.listOf (types.submodule {
           options = {
             port = mkOption {
-              type = types.int;
+              type = types.port;
               example = 8448;
               description = ''
                 The port to listen for HTTP(S) requests on.