diff --git a/index.bs b/index.bs
index a13c6520..42a3ca32 100644
--- a/index.bs
+++ b/index.bs
@@ -715,10 +715,12 @@ To <dfn>initialize WebTransport over HTTP</dfn>, given a {{WebTransport}} object
    and [=request/origin=] is |origin|.
 1. Run <a>report Content Security Policy violations for |request|</a>.
 1. If [=should request be blocked by Content Security Policy?=] with |request| returns
-   <b>blocked</b>, then abort the remaining steps and [=queue a network task=] with |transport|
+   <b>"Blocked"</b>, or if |request| [=block bad port|should be blocked due to a bad port=]
+   returns <b>blocked</b>, then abort the remaining steps and [=queue a network task=] with |transport|
    to run these steps:
   1. If |transport|'s [=[[State]]=] is `"closed"` or `"failed"`, then abort these steps.
-  1. Let |error| be a {{SecurityError}}.
+  1. Let |error| be the result of [=WebTransportError/creating=] a {{WebTransportError}} with
+     `"session"`.
   1. [=Cleanup=] |transport| with |error|, |error| and true.
 1. Let |networkPartitionKey| be the result of [=determining the network partition key=] with
    |transport|'s [=relevant settings object=].