diff --git a/server/server.py b/server/server.py
index cb31fe8..bce6385 100644
--- a/server/server.py
+++ b/server/server.py
@@ -22,7 +22,7 @@ import sys
 if sys.version_info.major <= 2:
     from cStringIO import StringIO
 else:
-    from io import StringIO
+    from io import BytesIO
 import time
 import json
 
@@ -34,7 +34,10 @@ app = Flask(__name__, static_url_path='', static_folder=os.path.abspath('../stat
 def predict():
     now = time.time()
     values = json.loads(request.data)
-    midi_data = pretty_midi.PrettyMIDI(StringIO(''.join(chr(v) for v in values)))
+    if sys.version_info.major <= 2:
+        midi_data = pretty_midi.PrettyMIDI(StringIO(''.join(chr(v) for v in values)))
+    else:
+        midi_data = pretty_midi.PrettyMIDI(BytesIO(b''.join([v.to_bytes(1,'big') for v in values])))
     duration = float(request.args.get('duration'))
     ret_midi = generate_midi(midi_data, duration)
     return send_file(ret_midi, attachment_filename='return.mid',