diff --git a/nix/modules/ec-node.nix b/nix/modules/ec-node.nix
index 50b0804..61be430 100644
--- a/nix/modules/ec-node.nix
+++ b/nix/modules/ec-node.nix
@@ -165,7 +165,7 @@ in
         };
 
         timeoutMs = lib.mkOption {
-          type = lib.types.ints.nonnegative;
+          type = lib.types.ints.u64;
           default = 30000;
           description = "Bridge run timeout; service restarts and refreshes gossip peers after this window (0 = run forever).";
         };