diff --git a/ext/fg/js/float.js b/ext/fg/js/float.js
index 8871160f..b42ab8ee 100644
--- a/ext/fg/js/float.js
+++ b/ext/fg/js/float.js
@@ -46,7 +46,7 @@ class DisplayFloat extends Display {
 
         this.setContentScale(scale);
 
-        window.parent.postMessage('initialized', '*');
+        apiForward('popupSetDisplayInitialized');
     }
 
     onError(error) {
diff --git a/ext/fg/js/frontend.js b/ext/fg/js/frontend.js
index 2286bf19..571bbf91 100644
--- a/ext/fg/js/frontend.js
+++ b/ext/fg/js/frontend.js
@@ -243,5 +243,6 @@ Frontend._windowMessageHandlers = new Map([
 ]);
 
 Frontend._runtimeMessageHandlers = new Map([
-    ['popupSetVisibleOverride', (self, {visible}) => { self.popup.setVisibleOverride(visible); }]
+    ['popupSetVisibleOverride', (self, {visible}) => { self.popup.setVisibleOverride(visible); }],
+    ['popupSetDisplayInitialized', (self) => { self.popup.setDisplayInitialized(); }]
 ]);
diff --git a/ext/fg/js/popup-proxy-host.js b/ext/fg/js/popup-proxy-host.js
index 427172c6..8ea70857 100644
--- a/ext/fg/js/popup-proxy-host.js
+++ b/ext/fg/js/popup-proxy-host.js
@@ -42,7 +42,8 @@ class PopupProxyHost {
             ['showContent', ({id, elementRect, writingMode, type, details}) => this._onApiShowContent(id, elementRect, writingMode, type, details)],
             ['setCustomCss', ({id, css}) => this._onApiSetCustomCss(id, css)],
             ['clearAutoPlayTimer', ({id}) => this._onApiClearAutoPlayTimer(id)],
-            ['setContentScale', ({id, scale}) => this._onApiSetContentScale(id, scale)]
+            ['setContentScale', ({id, scale}) => this._onApiSetContentScale(id, scale)],
+            ['setDisplayInitialized', ({id}) => this._onApiSetDisplayInitialized(id)]
         ]));
     }
 
@@ -103,6 +104,11 @@ class PopupProxyHost {
         return popup.setContentScale(scale);
     }
 
+    async _onApiSetDisplayInitialized(id) {
+        const popup = this._getPopup(id);
+        return popup.setDisplayInitialized();
+    }
+
     // Private functions
 
     _createPopupInternal(parentId, depth) {
diff --git a/ext/fg/js/popup-proxy.js b/ext/fg/js/popup-proxy.js
index 63aa6bbe..f1743064 100644
--- a/ext/fg/js/popup-proxy.js
+++ b/ext/fg/js/popup-proxy.js
@@ -102,6 +102,11 @@ class PopupProxy {
         this._invokeHostApi('setContentScale', {id, scale});
     }
 
+    async setDisplayInitialized() {
+        const id = await this._getPopupId();
+        this._invokeHostApi('setDisplayInitialized', {id});
+    }
+
     // Private
 
     _getPopupId() {
diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index ad4e5181..b8233cc2 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -43,8 +43,6 @@ class Popup {
         this._container.style.height = '0px';
 
         this._updateVisibility();
-
-        window.addEventListener('message', (e) => this.onMessage(e), false);
     }
 
     // Public properties
@@ -125,15 +123,7 @@ class Popup {
         this._invokeApi('setContentScale', {scale});
     }
 
-    onMessage(e) {
-        const action = e.data;
-        const handler = Popup._windowMessageHandlers.get(action);
-        if (typeof handler !== 'function') { return; }
-
-        handler(this);
-    }
-
-    setInitialized() {
+    setDisplayInitialized() {
         throw new Error('Override me');
     }
 
@@ -244,7 +234,7 @@ class Popup {
                     childrenSupported: this._childrenSupported,
                     scale: this._contentScale
                 });
-                this.setInitialized = resolve;
+                this.setDisplayInitialized = resolve;
             });
             this._observeFullscreen();
             this._onFullscreenChanged();
@@ -540,8 +530,4 @@ class Popup {
     }
 }
 
-Popup._windowMessageHandlers = new Map([
-    ['initialized', (self) => self.setInitialized()]
-]);
-
 Popup.outerStylesheet = null;