diff --git a/nixos/modules/services/networking/firefox-syncserver.nix b/nixos/modules/services/networking/firefox-syncserver.nix
index fa8e4fcaed2..52ed1c36153 100644
--- a/nixos/modules/services/networking/firefox-syncserver.nix
+++ b/nixos/modules/services/networking/firefox-syncserver.nix
@@ -19,6 +19,9 @@ let
       fxa_email_domain = "api.accounts.firefox.com";
       fxa_oauth_server_url = "https://oauth.accounts.firefox.com/v1";
       run_migrations = true;
+      # if JWK caching is not enabled the token server must verify tokens
+      # using the fxa api, on a thread pool with a static size.
+      additional_blocking_threads_for_fxa_requests = 10;
     } // lib.optionalAttrs cfg.singleNode.enable {
       # Single-node mode is likely to be used on small instances with little
       # capacity. The default value (0.1) can only ever release capacity when