diff --git a/Modules/FindFLTK.cmake b/Modules/FindFLTK.cmake
index bde27c4dd..8ad9d987e 100644
--- a/Modules/FindFLTK.cmake
+++ b/Modules/FindFLTK.cmake
@@ -28,6 +28,17 @@ FIND_PATH(FLTK_INCLUDE_PATH FL/Fl.h
 H:/usr/local/fltk
 )
 
+
+# Platform dependent libraries required by FLTK
+IF(WIN32)
+  SET( FLTK_PLATFORM_DEPENDENT_LIBS wsock32 )
+ENDIF(WIN32)
+
+IF(UNIX)
+  SET( FLTK_PLATFORM_DEPENDENT_LIBS ${CMAKE_X_LIBS}  -lm)
+ENDIF(UNIX)
+
+
 # Make sure that the FLTK include path has been set
 # So the FLTK_LIBRARY does not appear the first time
 IF(FLTK_INCLUDE_PATH)
@@ -58,7 +69,7 @@ IF(FLTK_INCLUDE_PATH)
     )
   ENDIF(USE_FLTK_VERSION_1.1)
 
-  SET( FLTK_LIBRARY ${FLTK_BASE_LIBRARY} ${FLTK_GL_LIBRARY} ${FLTK_FORMS_LIBRARY} ${FLTK_IMAGES_LIBRARY} )
+  SET( FLTK_LIBRARY ${FLTK_BASE_LIBRARY} ${FLTK_GL_LIBRARY} ${FLTK_FORMS_LIBRARY} ${FLTK_IMAGES_LIBRARY} ${FLTK_PLATFORM_DEPENDENT_LIBS} )
 
 ENDIF(FLTK_INCLUDE_PATH)