diff --git a/celery/worker/autoreload.py b/celery/worker/autoreload.py
index 03dcc8efd43..d4c687c3b0a 100644
--- a/celery/worker/autoreload.py
+++ b/celery/worker/autoreload.py
@@ -64,7 +64,7 @@ def register_with_event_loop(self, w, hub):
 def file_hash(filename, algorithm='md5'):
     hobj = hashlib.new(algorithm)
     with open(filename, 'rb') as f:
-        for chunk in iter(lambda: f.read(2 ** 20), ''):
+        for chunk in iter(lambda: f.read(2 ** 20), b''):
             hobj.update(ensure_bytes(chunk))
     return hobj.digest()