2 files changed, 15 insertions, 3 deletions
diff --git a/src/gui/image/qicon.cpp b/src/gui/image/qicon.cpp
index c362d0dc3f..d3090b89f2 100644
--- a/src/gui/image/qicon.cpp
+++ b/src/gui/image/qicon.cpp
@@ -1245,6 +1245,9 @@ QString QIcon::fallbackThemeName()
     themeSearchPath() containing an index.theme
     file describing its contents.
 
+    \note This should be done before creating \l QGuiApplication, to ensure
+    correct initialization.
+
     \sa fallbackThemeName(), themeSearchPaths(), themeName()
 */
 void QIcon::setFallbackThemeName(const QString &name)
diff --git a/src/gui/image/qiconloader.cpp b/src/gui/image/qiconloader.cpp
index 27c82bc09f..4420027049 100644
--- a/src/gui/image/qiconloader.cpp
+++ b/src/gui/image/qiconloader.cpp
@@ -112,10 +112,9 @@ extern QFactoryLoader *qt_iconEngineFactoryLoader(); // qicon.cpp
 void QIconLoader::ensureInitialized()
 {
     if (!m_initialized) {
+        if (!QGuiApplicationPrivate::platformTheme())
+            return; // it's too early: try again later (QTBUG-74252)
         m_initialized = true;
-
-        Q_ASSERT(qApp);
-
         m_systemTheme = systemThemeName();
 
         if (m_systemTheme.isEmpty())
@@ -125,6 +124,16 @@ void QIconLoader::ensureInitialized()
     }
 }
 
+/*!
+    \internal
+    Gets an instance.
+
+    \l QIcon::setFallbackThemeName() should be called before QGuiApplication is
+    created, to avoid a race condition (QTBUG-74252). When this function is
+    called from there, ensureInitialized() does not succeed because there
+    is no QPlatformTheme yet, so systemThemeName() is empty, and we don't want
+    m_systemTheme to get intialized to the fallback theme instead of the normal one.
+*/
 QIconLoader *QIconLoader::instance()
 {
    iconLoaderInstance()->ensureInitialized();