diff --git a/index.bs b/index.bs
index f39d69e4..2dce955a 100644
--- a/index.bs
+++ b/index.bs
@@ -5730,6 +5730,7 @@ are known as <dfn id="dfn-object-type" export>object types</dfn>.
         "async iterable" "&lt;" TypeWithExtendedAttributes "&gt;" Null
         "object" Null
         "symbol" Null
+        "ModuleNamespace" Null
         BufferRelatedType Null
         "FrozenArray" "&lt;" TypeWithExtendedAttributes "&gt;" Null
         "ObservableArray" "&lt;" TypeWithExtendedAttributes "&gt;" Null
@@ -6043,6 +6044,18 @@ To denote a type that includes all possible object references plus the
 <emu-val>null</emu-val> value, use the [=nullable type=]
 <code class="idl">object?</code>.
 
+<h4 id="idl-ModuleNamespace" interface>ModuleNamespace</h4>
+
+The {{ModuleNamespace}} type corresponds to the set of all possible non-null
+references to module namespace exotic objects as defined in the ECMAScript
+specification.
+
+There is no way to represent a constant {{ModuleNamespace}} value in IDL.
+
+To denote a type that includes all possible references to module namespace
+objects plus the <emu-val>null</emu-val> value, use the [=nullable type=]
+<code class="idl">ModuleNamespace?</code>.
+
 <h4 id="idl-symbol" interface>symbol</h4>
 
 The {{symbol}} type corresponds to the set of all possible symbol values. Symbol values are opaque,
@@ -7795,6 +7808,27 @@ values are represented by JavaScript Object values.
 </p>
 
 
+<h4 id="js-module-namespace" oldids="es-module-namespace">ModuleNamespace</h4>
+
+IDL {{ModuleNamespace}} values are represented by JavaScript module namespace exotic objects.
+
+<div id="js-to-module-namespace" algorithm="convert a JavaScript value to ModuleNamespace">
+    A JavaScript value |V| is [=converted to an IDL value|converted=] to an IDL {{ModuleNamespace}}
+    value by running the following algorithm:
+
+    1.  If |V| [=is not an Object=], or |V| is not a module namespace exotic object,
+        then [=JavaScript/throw=] a <l spec=ecmascript>{{TypeError}}</l>.
+    1.  Return the IDL {{ModuleNamespace}} value that is a reference
+        to the same object as |V|.
+</div>
+
+<p id="module-namespace-to-js">
+    The result of [=converted to a JavaScript value|converting=] an IDL {{ModuleNamespace}} value
+    to a JavaScript value is the Object value that represents a reference to the same object that
+    the IDL {{ModuleNamespace}} represents.
+</p>
+
+
 <h4 id="js-symbol" oldids="es-symbol">symbol</h4>
 
 IDL {{symbol}} values are represented by JavaScript Symbol values.