diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0577804..1f9d957 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -204,7 +204,7 @@
   set(CMAKE_REQUIRED_LIBRARIES ${FLTK_LIBRARIES})
 
   # FLTK STR #2599
-  check_cxx_source_compiles("#include <FL/Fl_Widget.H>\nint main(int c, char** v) { void *foo = (void*)&Fl_Widget::set_simple_keyboard; return 0; }" HAVE_FLTK_DEAD_KEYS)
+  check_cxx_source_compiles("#include <FL/Fl_Widget.H>\nint main(int c, char** v) { void (Fl_Widget::*foo)() = &Fl_Widget::set_simple_keyboard; return 0; }" HAVE_FLTK_DEAD_KEYS)
 
   # FLTK STR #2636
   check_cxx_source_compiles("#include <FL/Fl.H>\nint main(int c, char** v) { Fl::add_clipboard_notify(NULL, NULL); return 0; }" HAVE_FLTK_CLIPBOARD)