diff --git a/index.bs b/index.bs
index 93d0fee6..8f727b2b 100644
--- a/index.bs
+++ b/index.bs
@@ -1756,6 +1756,7 @@ This is a [=static command=].
           browserVersion: text,
           platformName: text,
           setWindowRect: bool,
+          userAgent: text,
           ? proxy: session.ProxyConfiguration,
           ? webSocketUrl: text,
           Extensible