diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8c532cb7a..3b8347473 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -41,7 +41,7 @@ set(FALKON_PLUGIN_PATH "${PLUGIN_PATH}" CACHE PATH "Default plugin search path")
 add_definitions(-DQT_NO_URL_CAST_FROM_STRING -DQT_USE_QSTRINGBUILDER -DQT_NO_CAST_TO_ASCII)
 
 # Mandatory: Qt5
-set(QT_MIN_VERSION "5.8.0")
+set(QT_MIN_VERSION "5.9.0")
 find_package(Qt5 ${QT_MIN_VERSION} REQUIRED COMPONENTS Core Widgets Network Sql QuickWidgets PrintSupport WebEngineWidgets WebChannel)
 if (BUILD_TESTING)
     find_package(Qt5 ${QT_MIN_VERSION} REQUIRED COMPONENTS Test)
diff --git a/src/lib/3rdparty/qtsingleapplication/qtlockedfile_win.cpp b/src/lib/3rdparty/qtsingleapplication/qtlockedfile_win.cpp
index bb30f83b4..f7a5ec4eb 100644
--- a/src/lib/3rdparty/qtsingleapplication/qtlockedfile_win.cpp
+++ b/src/lib/3rdparty/qtsingleapplication/qtlockedfile_win.cpp
@@ -66,24 +66,14 @@ Qt::HANDLE QtLockedFile::getMutexHandle(int idx, bool doCreate)
 
     Qt::HANDLE mutex;
     if (doCreate) {
-#if (QT_VERSION < 0x050000)
-        QT_WA( { mutex = CreateMutexW(NULL, FALSE, (TCHAR*)mname.utf16()); },
-        { mutex = CreateMutexA(NULL, FALSE, mname.toLocal8Bit().constData()); });
-#else // QT_WA removed from Qt5: http://qt-project.org/forums/viewthread/22994/#107379
         mutex = CreateMutexW(NULL, FALSE, (TCHAR*)mname.utf16());
-#endif
         if (!mutex) {
             qErrnoWarning("QtLockedFile::lock(): CreateMutex failed");
             return 0;
         }
     }
     else {
-#if (QT_VERSION < 0x050000)
-        QT_WA( { mutex = OpenMutexW(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, (TCHAR*)mname.utf16()); },
-        { mutex = OpenMutexA(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, mname.toLocal8Bit().constData()); });
-#else // QT_WA removed from Qt5: http://qt-project.org/forums/viewthread/22994/#107379
         mutex = OpenMutexW(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, (TCHAR*)mname.utf16());
-#endif
         if (!mutex) {
             if (GetLastError() != ERROR_FILE_NOT_FOUND) {
                 qErrnoWarning("QtLockedFile::lock(): OpenMutex failed");