diff --git a/includes/SkinVector.php b/includes/SkinVector.php
index 6eb807e2..0aa3108a 100644
--- a/includes/SkinVector.php
+++ b/includes/SkinVector.php
@@ -843,6 +843,7 @@ abstract class SkinVector extends SkinMustache {
 				$type = self::MENU_TYPE_DROPDOWN;
 				break;
 			case 'data-views':
+			case 'data-associated-pages':
 			case 'data-namespaces':
 				$type = self::MENU_TYPE_TABS;
 				break;
diff --git a/includes/templates/ArticleToolbar.mustache b/includes/templates/ArticleToolbar.mustache
index b7125533..0a8fa2fb 100644
--- a/includes/templates/ArticleToolbar.mustache
+++ b/includes/templates/ArticleToolbar.mustache
@@ -3,7 +3,7 @@
 	<div class="mw-article-toolbar-container">
 		{{#data-portlets}}
 		<div id="left-navigation">
-			{{#data-namespaces}}{{>Menu}}{{/data-namespaces}}
+			{{#data-associated-pages}}{{>Menu}}{{/data-associated-pages}}
 			{{#data-variants}}{{>Menu}}{{/data-variants}}
 		</div>
 		<div id="right-navigation" class="vector-collapsible {{#data-views.is-empty}}{{#data-actions.is-empty}}right-navigation-empty{{/data-actions.is-empty}}{{/data-views.is-empty}}">
diff --git a/resources/skins.vector.js/skin.js b/resources/skins.vector.js/skin.js
index 5e655a60..ec2b4132 100644
--- a/resources/skins.vector.js/skin.js
+++ b/resources/skins.vector.js/skin.js
@@ -36,6 +36,32 @@ function enableCssAnimations( document ) {
 	document.documentElement.classList.add( 'vector-animations-ready' );
 }
 
+/**
+ * In https://phabricator.wikimedia.org/T313409 #p-namespaces was renamed to #p-associatedPages
+ * This code maps items added by gadgets to the new menu.
+ * This code can be removed in MediaWiki 1.40.
+ */
+function addNamespacesGadgetSupport() {
+	// Set up hidden dummy portlet.
+	var dummyPortlet = document.createElement( 'div' );
+	dummyPortlet.setAttribute( 'id', 'p-namespaces' );
+	dummyPortlet.setAttribute( 'style', 'display: none;' );
+	dummyPortlet.appendChild( document.createElement( 'ul' ) );
+	document.body.appendChild( dummyPortlet );
+	mw.hook( 'util.addPortletLink' ).add( function ( /** @type {Element} */ node ) {
+		// If it was added to p-namespaces, show warning and move.
+		// eslint-disable-next-line no-jquery/no-global-selector
+		if ( $( '#p-namespaces' ).find( node ).length ) {
+			// eslint-disable-next-line no-jquery/no-global-selector
+			$( '#p-associated-pages ul' ).append( node );
+			// @ts-ignore
+			mw.log.warn( 'Please update call to mw.util.addPortletLink with ID p-namespaces. Use p-associatedPages instead.' );
+			// in case it was empty before:
+			mw.util.showPortlet( 'p-associated-pages' );
+		}
+	} );
+}
+
 /**
  * @param {Window} window
  * @return {void}
@@ -47,6 +73,7 @@ function main( window ) {
 	initSearchLoader( document );
 	languageButton();
 	dropdownMenus();
+	addNamespacesGadgetSupport();
 }
 
 /**
diff --git a/skin.json b/skin.json
index 0f90a9ea..841cca02 100644
--- a/skin.json
+++ b/skin.json
@@ -41,6 +41,16 @@
 						"skin-vector",
 						"skin-vector-search-vue"
 					],
+					"menus": [
+						"user-interface-preferences",
+						"user-page",
+						"user-menu",
+						"notifications",
+						"views",
+						"actions",
+						"variants",
+						"associated-pages"
+					],
 					"scripts": [
 						"skins.vector.user",
 						"skins.vector.js",