diff -urp mathgl-2.4.1/CMakeLists.txt mathgl-2.4.1-fluid/CMakeLists.txt
--- mathgl-2.4.1/CMakeLists.txt	2017-12-05 11:49:15.767073586 +0700
+++ mathgl-2.4.1-fluid/CMakeLists.txt	2017-12-05 11:53:07.085161409 +0700
@@ -556,6 +556,7 @@ endif(enable-glut)
 
 if(enable-fltk)
 	set(MGL_HAVE_FLTK 1)
+	set(FLTK_SKIP_FLUID 1)
 	FIND_PACKAGE(FLTK)
 	if(NOT FLTK_FOUND)
 		message(SEND_ERROR "Couldn't find FLTK library.")