diff --git a/S3/FileLists.py b/S3/FileLists.py
index 823b4cea..5a97346f 100644
--- a/S3/FileLists.py
+++ b/S3/FileLists.py
@@ -172,10 +172,10 @@ def _append(d, key, value):
         try:
             f = None
             if fname == u'-':
-                f = io.open(sys.stdin.fileno(), mode='r', closefd=False)
+                f = io.open(sys.stdin.fileno(), mode='rb', closefd=False)
             else:
                 try:
-                    f = io.open(deunicodise(fname), mode='r')
+                    f = io.open(deunicodise(fname), mode='rb')
                 except IOError as e:
                     warning(u"--files-from input file %s could not be opened for reading (%s), skipping." % (fname, e.strerror))
                     continue