diff --git a/index.bs b/index.bs
index 809c06dd..09d942a3 100644
--- a/index.bs
+++ b/index.bs
@@ -2046,7 +2046,7 @@ BrowserResult = (
Each [=/top-level traversable=] is associated with a single client
window which represents a rectangular area containing the
-viewport that will be used to render that [=/top-level
+viewport that will be used to render that [=/top-level
traversable=]'s [=active document=] when its [=visibility state=] is
"visible
", as well as any browser-specific user interface elements
associated with displaying the traversable (e.g. any URL bar, toolbars, or OS