diff --git a/src/corelib/kernel/qeventdispatcher_wasm.cpp b/src/corelib/kernel/qeventdispatcher_wasm.cpp
index 5f4c46c07f2..f5061f35d74 100644
--- a/src/corelib/kernel/qeventdispatcher_wasm.cpp
+++ b/src/corelib/kernel/qeventdispatcher_wasm.cpp
@@ -218,9 +218,12 @@ QEventDispatcherWasm::QEventDispatcherWasm()
 #if QT_CONFIG(thread)
         g_mainThread = pthread_self();
 #endif
+
         // Call the "onLoaded" JavaScript callback, unless startup tasks
-        // have been registered which should complete first.
-        checkCallQtLoaded();
+        // have been registered which should complete first. Run async
+        // to make sure event dispatcher construction (in particular any
+        // subclass construction) has completed first.
+        runAsync(callOnLoadedIfRequired);
     } else {
 #if QT_CONFIG(thread)
         std::lock_guard<std::mutex> lock(g_staticDataMutex);
@@ -916,10 +919,10 @@ void QEventDispatcherWasm::registerStartupTask()
 void QEventDispatcherWasm::completeStarupTask()
 {
     --g_startupTasks;
-    checkCallQtLoaded();
+    callOnLoadedIfRequired();
 }
 
-void QEventDispatcherWasm::checkCallQtLoaded()
+void QEventDispatcherWasm::callOnLoadedIfRequired()
 {
     if (g_startupTasks > 0)
         return;
@@ -929,12 +932,16 @@ void QEventDispatcherWasm::checkCallQtLoaded()
         return;
     qtLoadedCalled = true;
 
-    QTimer::singleShot(0, [](){
-        emscripten::val qt = emscripten::val::module_property("qt");
-        if (qt.isUndefined())
-            return;
-        qt.call<void>("onLoaded");
-    });
+    Q_ASSERT(g_mainThreadEventDispatcher);
+    g_mainThreadEventDispatcher->onLoaded();
+}
+
+void QEventDispatcherWasm::onLoaded()
+{
+    emscripten::val qt = emscripten::val::module_property("qt");
+    if (qt.isUndefined())
+        return;
+    qt.call<void>("onLoaded");
 }
 
 namespace {
diff --git a/src/corelib/kernel/qeventdispatcher_wasm_p.h b/src/corelib/kernel/qeventdispatcher_wasm_p.h
index afffc8a813b..0d94c48a25d 100644
--- a/src/corelib/kernel/qeventdispatcher_wasm_p.h
+++ b/src/corelib/kernel/qeventdispatcher_wasm_p.h
@@ -59,7 +59,8 @@ public:
 
     static void registerStartupTask();
     static void completeStarupTask();
-    static void checkCallQtLoaded();
+    static void callOnLoadedIfRequired();
+    virtual void onLoaded();
 
 protected:
     virtual bool processPostedEvents();
diff --git a/src/plugins/platforms/wasm/qwasmcompositor.cpp b/src/plugins/platforms/wasm/qwasmcompositor.cpp
index 66eaea62faa..48445d5db95 100644
--- a/src/plugins/platforms/wasm/qwasmcompositor.cpp
+++ b/src/plugins/platforms/wasm/qwasmcompositor.cpp
@@ -4,6 +4,8 @@
 #include "qwasmcompositor.h"
 #include "qwasmwindow.h"
 
+#include <private/qeventdispatcher_wasm_p.h>
+
 #include <qpa/qwindowsysteminterface.h>
 
 #include <emscripten/html5.h>
@@ -41,6 +43,17 @@ void QWasmCompositor::setEnabled(bool enabled)
     m_isEnabled = enabled;
 }
 
+// requestUpdate delivery is initially disabled at startup, while Qt completes
+// startup tasks such as font loading. This function enables requestUpdate delivery
+// again.
+void QWasmCompositor::releaseRequesetUpdateHold()
+{
+    if (!m_requestUpdateHoldEnabled)
+        return;
+    m_requestUpdateHoldEnabled = false;
+    requestUpdate();
+}
+
 void QWasmCompositor::requestUpdateWindow(QWasmWindow *window, UpdateRequestDeliveryType updateType)
 {
     auto it = m_requestUpdateWindows.find(window);
@@ -62,6 +75,9 @@ void QWasmCompositor::requestUpdate()
     if (m_requestAnimationFrameId != -1)
         return;
 
+    if (m_requestUpdateHoldEnabled)
+        return;
+
     static auto frame = [](double frameTime, void *context) -> int {
         Q_UNUSED(frameTime);
 
diff --git a/src/plugins/platforms/wasm/qwasmcompositor.h b/src/plugins/platforms/wasm/qwasmcompositor.h
index 182ea2b1678..5de401844c3 100644
--- a/src/plugins/platforms/wasm/qwasmcompositor.h
+++ b/src/plugins/platforms/wasm/qwasmcompositor.h
@@ -31,8 +31,8 @@ public:
     QWasmScreen *screen();
     void setEnabled(bool enabled);
 
+    void releaseRequesetUpdateHold();
     enum UpdateRequestDeliveryType { ExposeEventDelivery, UpdateRequestDelivery };
-
     void requestUpdateWindow(QWasmWindow *window, UpdateRequestDeliveryType updateType = ExposeEventDelivery);
 
     void handleBackingStoreFlush(QWindow *window);
@@ -50,6 +50,7 @@ private:
     bool m_isEnabled = true;
     QMap<QWasmWindow *, UpdateRequestDeliveryType> m_requestUpdateWindows;
     int m_requestAnimationFrameId = -1;
+    bool m_requestUpdateHoldEnabled = true;
     bool m_inDeliverUpdateRequest = false;
 };
 
diff --git a/src/plugins/platforms/wasm/qwasmeventdispatcher.cpp b/src/plugins/platforms/wasm/qwasmeventdispatcher.cpp
index cd2cefc14d9..1f2d3095d65 100644
--- a/src/plugins/platforms/wasm/qwasmeventdispatcher.cpp
+++ b/src/plugins/platforms/wasm/qwasmeventdispatcher.cpp
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
 
 #include "qwasmeventdispatcher.h"
+#include "qwasmintegration.h"
 
 #include <QtGui/qpa/qwindowsysteminterface.h>
 
@@ -15,4 +16,20 @@ bool QWasmEventDispatcher::processPostedEvents()
     return QWindowSystemInterface::sendWindowSystemEvents(QEventLoop::AllEvents);
 }
 
+void QWasmEventDispatcher::onLoaded()
+{
+    // This function is called when the application is ready to paint
+    // the first frame. Send the qtlaoder onLoaded event first (via
+    // the base class implementation), and then enable/call requestUpdate
+    // to deliver a frame.
+    QEventDispatcherWasm::onLoaded();
+
+    // Make sure all screens have a defined size; and pick
+    // up size changes due to onLoaded event handling.
+    QWasmIntegration *wasmIntegration = QWasmIntegration::get();
+    wasmIntegration->resizeAllScreens();
+
+    wasmIntegration->releaseRequesetUpdateHold();
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/wasm/qwasmeventdispatcher.h b/src/plugins/platforms/wasm/qwasmeventdispatcher.h
index 33d672a57fb..cbf10482e3f 100644
--- a/src/plugins/platforms/wasm/qwasmeventdispatcher.h
+++ b/src/plugins/platforms/wasm/qwasmeventdispatcher.h
@@ -12,6 +12,7 @@ class QWasmEventDispatcher : public QEventDispatcherWasm
 {
 protected:
     bool processPostedEvents() override;
+    void onLoaded() override;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/wasm/qwasmintegration.cpp b/src/plugins/platforms/wasm/qwasmintegration.cpp
index c665251d0d2..d2e7c8716cc 100644
--- a/src/plugins/platforms/wasm/qwasmintegration.cpp
+++ b/src/plugins/platforms/wasm/qwasmintegration.cpp
@@ -206,6 +206,13 @@ void QWasmIntegration::removeBackingStore(QWindow* window)
     m_backingStores.remove(window);
 }
 
+void QWasmIntegration::releaseRequesetUpdateHold()
+{
+    for (const auto &elementAndScreen : m_screens) {
+        elementAndScreen.wasmScreen->compositor()->releaseRequesetUpdateHold();
+    }
+}
+
 #ifndef QT_NO_OPENGL
 QPlatformOpenGLContext *QWasmIntegration::createPlatformOpenGLContext(QOpenGLContext *context) const
 {
diff --git a/src/plugins/platforms/wasm/qwasmintegration.h b/src/plugins/platforms/wasm/qwasmintegration.h
index eeb68109a0d..870bd0d16b4 100644
--- a/src/plugins/platforms/wasm/qwasmintegration.h
+++ b/src/plugins/platforms/wasm/qwasmintegration.h
@@ -78,6 +78,7 @@ public:
     void resizeAllScreens();
     void loadLocalFontFamilies(emscripten::val families);
     void removeBackingStore(QWindow* window);
+    void releaseRequesetUpdateHold();
     static quint64 getTimestamp();
 
     int touchPoints;