diff --git a/index.bs b/index.bs
index 183a18d4..b004a123 100644
--- a/index.bs
+++ b/index.bs
@@ -11338,7 +11338,7 @@ To <dfn>expand a extension data spec</dfn> given |extension data spec|:
 
 1. Let |installation type| be a value of <code>type</code> field of |extension data spec|.
 
-1. If installing |installation type| isn't supported return [=error=] with error code [=unsupported operation=].
+1. If installing |installation type| isn't supported return [=error=] with [=error code=] [=unsupported operation=].
 
 1. Switch on the value of the <code>installation type</code>: