diff --git a/spec.bs b/spec.bs
index e9ef60b5..3738cd8a 100644
--- a/spec.bs
+++ b/spec.bs
@@ -422,8 +422,10 @@ To <dfn>check interest group permissions</dfn> given an [=origin=]
 1. Let |permissions| be the result of [=parsing JSON bytes to an Infra value=] with |resource|,
   returning false on failure.
 1. If |permissions| is not an [=ordered map=], then return false.
-1. If |joinOrLeave| is "`join`" and |permissions|["`joinAdInterestGroup`"] [=map/exists=], then
-  return |permissions|["`joinAdInterestGroup`"].
+1. Set |joinPermission| to false.
+1. If |permissions|["`joinAdInterestGroup`"] [=map/exists=] set |joinPermission| to |permissions|["`joinAdInterestGroup`"].
+1. If |joinOrLeave| is "`join`" return |joinPermission|.
+1. If |joinOrLeave| is "`leave`" and |joinPermission| is true, return true.
 1. If |joinOrLeave| is "`leave`" and |permissions|["`leaveAdInterestGroup`"] [=map/exists=], then
   return |permissions|["`leaveAdInterestGroup`"].
 1. Return false.