diff --git a/src/Main/Makefile.am b/src/Main/Makefile.am
index db58cab4a..774999354 100644
--- a/src/Main/Makefile.am
+++ b/src/Main/Makefile.am
@@ -11,9 +11,9 @@ THREAD_LIBS =
 endif
 
 if USE_SDL
-GFX_SOURCES = fg_os_sdl.cxx fg_os.hxx
+GFX_CODE = fg_os_sdl.cxx fg_os.hxx
 else
-GFX_SOURCES = fg_os.cxx fg_os.hxx
+GFX_CODE = fg_os.cxx fg_os.hxx
 endif
 
 if FG_USE_CLOUDS_3D
@@ -47,7 +47,7 @@ libMain_a_SOURCES = \
 	util.cxx util.hxx \
 	viewer.cxx viewer.hxx \
 	viewmgr.cxx viewmgr.hxx \
-	$(GFX_SOURCES)
+	$(GFX_CODE)
 
 fgfs_SOURCES = bootstrap.cxx