diff --git a/libisoburn/trunk/xorriso/README b/libisoburn/trunk/xorriso/README
index e7f52e50..0f844691 100644
--- a/libisoburn/trunk/xorriso/README
+++ b/libisoburn/trunk/xorriso/README
@@ -120,10 +120,13 @@ on disk. It uses the normal POSIX filesystem calls, i.e. no libburnia stuff.
 
 This program is not installed systemwide but stays in the installation
 directory of the xorriso tarball as  test/compare_file . Usually it is
-run as -exec payload of a find command. It takes three arguments:
+run as -exec payload of a find command. It demands at least three arguments:
 The path of the first file to compare, the prefix1 to be cut off from path
 and the prefix2 which gets prepended afterwards to obtain the path of the
 second file to compare.
+As further argument there can be -no_ctime which suppresses the comparison
+of ctime date stamps.
+The exit value is 0 if no difference was detected, non-0 else.
 
 Example: After
    xorriso ... -pathspecs on -add /=/original/dir --