diff --git a/index.bs b/index.bs
index 4d01fe35..0cb9fa68 100644
--- a/index.bs
+++ b/index.bs
@@ -466,10 +466,10 @@ in the ResultData
group for the results of commands in the module.
Modules which contain events define [=local end definition=] fragments that are
choices in the Event
group for the module's [=events=].
-An implementation may define extension modules. These must have a
+An implementation may define extension modules. These must have a
[=module name=] that contains a single colon ":
" character. The
part before the colon is the prefix; this is typically the same for all
-extension modules specific to a given implementation and should be unique for a
+[=extension modules=] specific to a given implementation and should be unique for a
given implementation. Such modules extend the [=local end definition=] and [=remote end definition=]
providing additional groups as choices for the defined [=commands=] and [=events=].