diff --git a/Modules/FindFLTK.cmake b/Modules/FindFLTK.cmake
index 25ddb189c7..8edc00b2fc 100644
--- a/Modules/FindFLTK.cmake
+++ b/Modules/FindFLTK.cmake
@@ -45,7 +45,7 @@ IF(WIN32)
 ENDIF(WIN32)
 
 IF(UNIX)
-  INCLUDE(${CMAKE_ROOT}/Modules/FindX11.cmake)
+  INCLUDE(FindX11)
   FIND_LIBRARY(FLTK_MATH_LIBRARY m)
   SET( FLTK_PLATFORM_DEPENDENT_LIBS ${X11_LIBRARIES} ${FLTK_MATH_LIBRARY})
 ENDIF(UNIX)