diff --git a/youtube_dl/aes.py b/youtube_dl/aes.py
index 07224d508..7817adcfd 100644
--- a/youtube_dl/aes.py
+++ b/youtube_dl/aes.py
@@ -152,7 +152,7 @@ def aes_decrypt_text(data, password, key_size_bytes):
     """
     NONCE_LENGTH_BYTES = 8
 
-    data = bytes_to_intlist(base64.b64decode(data))
+    data = bytes_to_intlist(base64.b64decode(data.encode('utf-8')))
     password = bytes_to_intlist(password.encode('utf-8'))
 
     key = password[:key_size_bytes] + [0] * (key_size_bytes - len(password))