diff --git a/rhodecode/lib/_vendor/authomatic/adapters.py b/rhodecode/lib/_vendor/authomatic/adapters.py
--- a/rhodecode/lib/_vendor/authomatic/adapters.py
+++ b/rhodecode/lib/_vendor/authomatic/adapters.py
@@ -271,8 +271,7 @@ class WerkzeugAdapter(BaseAdapter):
         self.response = response
 
     def write(self, value):
-        #self.response.data = self.response.data.decode('utf-8') + value
-        self.response.data = self.response.data + value
+        self.response.data = self.response.data.decode('utf-8') + value
 
     def set_header(self, key, value):
         self.response.headers[key] = value
diff --git a/rhodecode/lib/_vendor/authomatic/core.py b/rhodecode/lib/_vendor/authomatic/core.py
--- a/rhodecode/lib/_vendor/authomatic/core.py
+++ b/rhodecode/lib/_vendor/authomatic/core.py
@@ -1159,8 +1159,7 @@ class Response(ReprMixin):
             if self.is_binary_string(content):
                 self._content = content
             else:
-                #self._content = content.decode('utf-8')
-                self._content = content
+                self._content = content.decode('utf-8')
         return self._content
 
     @property