diff --git a/src/resources.py b/src/resources.py
index 9d7e443..684ece8 100644
--- a/src/resources.py
+++ b/src/resources.py
@@ -75,7 +75,7 @@ class SampleResource(Resource):
                         'wave.wav',
                         soundfile,
                         soundfile.content_type,
-                        {'Content-Length': len(soundfile)})})
+                        {'Content-Length': soundfile.content_length})})
             rabbitmq_channel.basic_publish(
                 exchange=RABBITMQ_EXCHANGE,
                 routing_key='feature',