diff --git a/development/cmake/ConfigureChecks.cmake b/development/cmake/ConfigureChecks.cmake
index 1b6bf45bd0..5dc0bc52e8 100644
--- a/development/cmake/ConfigureChecks.cmake
+++ b/development/cmake/ConfigureChecks.cmake
@@ -275,7 +275,7 @@ if(LYX_USE_QT MATCHES "QT5")
     set(lyx_qt5_config "QtCore/qconfig.h")
   endif()
   if(WIN32)
-    set(QT_USES_X11 CACHE "Win32 compiled without X11" 0)
+    set(QT_USES_X11 OFF BOOL CACHE "Win32 compiled without X11")
     # The try_run for minngw would not work here anyway
   else()
     check_cxx_source_runs(