--- a/build/cmake/functions.cmake
+++ b/build/cmake/functions.cmake
@@ -1057,6 +1057,7 @@ endfunction()
 # The default is ON if not third parameter is specified
 function(wx_option name desc)
     cmake_parse_arguments(OPTION "" "" "STRINGS" ${ARGN})
+    set(OPTION_STRINGS OFF)
     if(ARGC EQUAL 2)
         set(default ON)
     else()