commit 6974b7ce407cd5c8b55834535fe2438fd067b3d6
Author: Jonathan Hamilton <jtrhamilton@gmail.com>
Date:   Thu Apr 9 21:43:24 2015 -0700

    We're only reading 5 bytes of magic, so only compare 5

diff --git a/src/archiver_iso9660.c b/src/archiver_iso9660.c
index f4fe63a..e7d5362 100644
--- a/src/archiver_iso9660.c
+++ b/src/archiver_iso9660.c
@@ -554,7 +554,7 @@ static void *ISO9660_openArchive(PHYSFS_Io *io, const char *filename, int forWri
     /* Skip system area to magic number in Volume descriptor */
     BAIL_IF_MACRO(!io->seek(io, 32769), ERRPASS, NULL);
     BAIL_IF_MACRO(io->read(io, magicnumber, 5) != 5, ERRPASS, NULL);
-    if (memcmp(magicnumber, "CD001", 6) != 0)
+    if (memcmp(magicnumber, "CD001", 5) != 0)
         BAIL_MACRO(PHYSFS_ERR_UNSUPPORTED, NULL);
 
     handle = allocator.Malloc(sizeof(ISO9660Handle));