diff --git a/config/qt.m4 b/config/qt.m4
index 6a455f9134..93b8575ad3 100644
--- a/config/qt.m4
+++ b/config/qt.m4
@@ -217,31 +217,15 @@ AC_DEFUN([QT_DO_IT_ALL],
 	     fi;;
 	esac
 
+	dnl Specific support for X11 will be built if these are available
+	AC_CHECK_HEADERS([xcb/xcb.h])
+	AC_CHECK_LIB([xcb], [xcb_send_event])
 
 	save_CPPFLAGS=$CPPFLAGS
 	CPPFLAGS="$save_CPPFLAGS $QT_CORE_INCLUDES"
 	AC_CHECK_HEADER(QtGui/qtgui-config.h,
 	  [lyx_qt_config=QtGui/qtgui-config.h],
 	  [lyx_qt_config=qconfig.h])
-	AC_MSG_CHECKING([whether Qt uses the X Window system])
-	if test x$USE_QT6 = xyes ; then
-	  dnl FIXME: Check whether defining QPA_XCB makes sense with Qt6
-	  AC_PREPROC_IFELSE([AC_LANG_SOURCE([
-	    [#include <$lyx_qt_config>]
-	    [#if !defined(QT_FEATURE_xcb) || QT_FEATURE_xcb < 0]
-	    [#error Fail]
-	    [#endif]])],
-	    [AC_MSG_RESULT(yes)
-	     AC_DEFINE(QPA_XCB, 1, [Define if Qt uses the X Window System])],
-	    [AC_MSG_RESULT(no)])
-	else
-	  AC_EGREP_CPP(xcb,
-	    [#include <$lyx_qt_config>
-	    QT_QPA_DEFAULT_PLATFORM_NAME],
-	    [AC_MSG_RESULT(yes)
-	     AC_DEFINE(QPA_XCB, 1, [Define if Qt uses the X Window System])],
-	    [AC_MSG_RESULT(no)])
-	fi
 	CPPFLAGS=$save_CPPFLAGS
 
 	QT_FIND_TOOL([QT_MOC], [moc])
diff --git a/src/frontends/qt/GuiApplication.cpp b/src/frontends/qt/GuiApplication.cpp
index f7eabe276c..00648c1561 100644
--- a/src/frontends/qt/GuiApplication.cpp
+++ b/src/frontends/qt/GuiApplication.cpp
@@ -121,7 +121,7 @@
 #include <QThreadPool>
 #include <QWidget>
 
-#if defined(QPA_XCB)
+#ifdef HAVE_XCB_XCB_H
 #include <xcb/xcb.h>
 #ifdef HAVE_QT5_X11_EXTRAS
 #include <QtX11Extras/QX11Info>
@@ -1157,10 +1157,14 @@ GuiApplication::GuiApplication(int & argc, char ** argv)
 	// Install Qt native translator for GUI elements.
 	installTranslator(&d->qt_trans_);
 
-#ifdef QPA_XCB
-	// Enable reception of XCB events.
-	installNativeEventFilter(this);
+	if (platformName() == "xcb") {
+#if defined(HAVE_XCB_XCB_H) && defined(HAVE_LIBXCB)
+		// Enable reception of XCB events.
+		installNativeEventFilter(this);
+#else
+		LYXERR0("Warning: X11 support is incomplete in this LyX binary.");
 #endif
+	}
 
 	// FIXME: quitOnLastWindowClosed is true by default. We should have a
 	// lyxrc setting for this in order to let the application stay resident.
@@ -1181,13 +1185,13 @@ GuiApplication::GuiApplication(int & argc, char ** argv)
 			this, SLOT(onApplicationStateChanged(Qt::ApplicationState)));
 #endif
 
-#if defined(QPA_XCB)
-	// doubleClickInterval() is 400 ms on X11 which is just too long.
-	// On Windows and Mac OS X, the operating system's value is used.
-	// On Microsoft Windows, calling this function sets the double
-	// click interval for all applications. So we don't!
-	QApplication::setDoubleClickInterval(300);
-#endif
+	if (platformName() == "xcb") {
+		// doubleClickInterval() is 400 ms on X11 which is just too long.
+		// On Windows and Mac OS X, the operating system's value is used.
+		// On Microsoft Windows, calling this function sets the double
+		// click interval for all applications. So we don't!
+		QApplication::setDoubleClickInterval(300);
+	}
 
 	connect(this, SIGNAL(lastWindowClosed()), this, SLOT(onLastWindowClosed()));
 
@@ -3498,7 +3502,7 @@ bool GuiApplication::longOperationStarted() {
 //
 // X11 specific stuff goes here...
 
-#if defined(QPA_XCB)
+#if defined(HAVE_XCB_XCB_H) && defined(HAVE_LIBXCB)
 bool GuiApplication::nativeEventFilter(const QByteArray & eventType,
 				       void * message, QINTPTR *)
 {
diff --git a/src/frontends/qt/GuiApplication.h b/src/frontends/qt/GuiApplication.h
index 38c3c0a6e0..a2fce4d6fe 100644
--- a/src/frontends/qt/GuiApplication.h
+++ b/src/frontends/qt/GuiApplication.h
@@ -20,7 +20,7 @@
 
 #include <QApplication>
 #include <QList>
-#ifdef QPA_XCB
+#if defined(HAVE_XCB_XCB_H) && defined(HAVE_LIBXCB)
 #include <QAbstractNativeEventFilter>
 #endif
 
@@ -53,7 +53,7 @@ There should be only one instance of this class. No Qt object
 initialisation should be done before the instantiation of this class.
 */
 class GuiApplication : public QApplication, public Application
-#ifdef QPA_XCB
+#if defined(HAVE_XCB_XCB_H) && defined(HAVE_LIBXCB)
 		     , public QAbstractNativeEventFilter
 #endif
 {
@@ -121,7 +121,7 @@ public:
 	//@{
 	bool notify(QObject * receiver, QEvent * event) override;
 	void commitData(QSessionManager & sm);
-#if defined(QPA_XCB)
+#if defined(HAVE_XCB_XCB_H) && defined(HAVE_LIBXCB)
 #if (QT_VERSION < 0x060000)
 #define QINTPTR long
 #else