diff --git a/beetsplug/spotify.py b/beetsplug/spotify.py
index caaa06a55..88a584f86 100644
--- a/beetsplug/spotify.py
+++ b/beetsplug/spotify.py
@@ -68,8 +68,8 @@ class SpotifyPlugin(BeetsPlugin):
             'Authorization': 'Basic {}'.format(
                 base64.b64encode(
                     '{}:{}'.format(
-                        self.config['client_id'].as_str(),
-                        self.config['client_secret'].as_str(),
+                        bytes(self.config['client_id'].as_str()),
+                        bytes(self.config['client_secret'].as_str()),
                     )
                 )
             )