diff --git a/src/gui/image/qiconloader.cpp b/src/gui/image/qiconloader.cpp
index 629d59d535e..da02582338b 100644
--- a/src/gui/image/qiconloader.cpp
+++ b/src/gui/image/qiconloader.cpp
@@ -168,6 +168,7 @@ void QIconLoader::setFallbackThemeName(const QString &themeName)
 {
     qCDebug(lcIconLoader) << "Setting fallback theme name to" << themeName;
     m_userFallbackTheme = themeName;
+    invalidateKey();
 }
 
 void QIconLoader::setThemeSearchPath(const QStringList &searchPaths)
diff --git a/tests/auto/gui/image/qicon/CMakeLists.txt b/tests/auto/gui/image/qicon/CMakeLists.txt
index c900c60d5b5..2d212defb78 100644
--- a/tests/auto/gui/image/qicon/CMakeLists.txt
+++ b/tests/auto/gui/image/qicon/CMakeLists.txt
@@ -56,6 +56,8 @@ set(tst_qicon_resource_files
     "./icons/themeparent/index.theme"
     "./icons/themeparent/scalable/actions/address-book-new.svg"
     "./icons/themeparent/scalable/actions/appointment-new.svg"
+    "./icons/fallbacktheme/index.theme"
+    "./icons/fallbacktheme/16x16/edit-cut.png"
     "./second_icons/testtheme/32x32/actions/appointment-new.png"
     "./styles/commonstyle/images/standardbutton-open-128.png"
     "./styles/commonstyle/images/standardbutton-open-16.png"
diff --git a/tests/auto/gui/image/qicon/icons/fallbacktheme/16x16/edit-cut.png b/tests/auto/gui/image/qicon/icons/fallbacktheme/16x16/edit-cut.png
new file mode 100644
index 00000000000..661ef1ad030
Binary files /dev/null and b/tests/auto/gui/image/qicon/icons/fallbacktheme/16x16/edit-cut.png differ
diff --git a/tests/auto/gui/image/qicon/icons/fallbacktheme/index.theme b/tests/auto/gui/image/qicon/icons/fallbacktheme/index.theme
new file mode 100644
index 00000000000..809d2966690
--- /dev/null
+++ b/tests/auto/gui/image/qicon/icons/fallbacktheme/index.theme
@@ -0,0 +1,8 @@
+[Icon Theme]
+Name=fallbacktheme
+
+Directories=16x16
+
+[16x16]
+Size=16
+Type=Fixed
diff --git a/tests/auto/gui/image/qicon/tst_qicon.cpp b/tests/auto/gui/image/qicon/tst_qicon.cpp
index ebb0f1e9d2c..4b104490687 100644
--- a/tests/auto/gui/image/qicon/tst_qicon.cpp
+++ b/tests/auto/gui/image/qicon/tst_qicon.cpp
@@ -717,6 +717,11 @@ void tst_QIcon::fromTheme()
         QCOMPARE(i.availableSizes(), abIcon.availableSizes());
     }
 
+    // Check that setting a fallback theme invalidates earlier lookups
+    QVERIFY(QIcon::fromTheme("edit-cut").isNull());
+    QIcon::setFallbackThemeName("fallbacktheme");
+    QVERIFY(!QIcon::fromTheme("edit-cut").isNull());
+
     // Make sure setting the theme name clears the state
     QIcon::setThemeName("");
     abIcon = QIcon::fromTheme("address-book-new");
@@ -725,6 +730,9 @@ void tst_QIcon::fromTheme()
     // Passing a full path to fromTheme is not very useful, but should work anyway
     QIcon fullPathIcon = QIcon::fromTheme(m_pngImageFileName);
     QVERIFY(!fullPathIcon.isNull());
+
+    // Restore to system fallback theme
+    QIcon::setFallbackThemeName("");
 }
 
 static inline QString findGtkUpdateIconCache()