diff --git a/src/gateway/index.ts b/src/gateway/index.ts
index c3e5a5e..fcc1c3f 100644
--- a/src/gateway/index.ts
+++ b/src/gateway/index.ts
@@ -216,7 +216,11 @@ export default function(server: Server) {
                     break;
                 }
                 case GatewayPayloadType.Ping: {
-                    // TODO: also check session here and ensure packet is sent at the right time
+                    if (payload.d !== 0) {
+                        return closeWithBadPayload(ws, "d: expected numeric '0'");
+                    }
+
+                    // TODO: also check session here
                     ws.state.alive = true;
                     break;
                 }