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.")