diff --git a/gcc/include/filenames.h b/gcc/include/filenames.h
index 795d6b2092..066ac099ed 100644
--- a/gcc/include/filenames.h
+++ b/gcc/include/filenames.h
@@ -41,11 +41,13 @@ extern "C" {
 #  define IS_DIR_SEPARATOR(c) IS_DOS_DIR_SEPARATOR (c)
 #  define IS_ABSOLUTE_PATH(f) IS_DOS_ABSOLUTE_PATH (f)
 #else /* not DOSish */
-//#  if defined(__APPLE__)
-//#    ifndef HAVE_CASE_INSENSITIVE_FILE_SYSTEM
-//#      define HAVE_CASE_INSENSITIVE_FILE_SYSTEM 1
-//#    endif
-//#  endif /* __APPLE__ */
+#  if defined(__APPLE__)
+/*
+#    ifndef HAVE_CASE_INSENSITIVE_FILE_SYSTEM
+#      define HAVE_CASE_INSENSITIVE_FILE_SYSTEM 1
+#    endif
+*/
+#  endif /* __APPLE__ */
 #  define HAS_DRIVE_SPEC(f) (0)
 #  define IS_DIR_SEPARATOR(c) IS_UNIX_DIR_SEPARATOR (c)
 #  define IS_ABSOLUTE_PATH(f) IS_UNIX_ABSOLUTE_PATH (f)