diff --git a/pagure/lib/mimetype.py b/pagure/lib/mimetype.py
index bd270bc..4798a75 100644
--- a/pagure/lib/mimetype.py
+++ b/pagure/lib/mimetype.py
@@ -58,11 +58,11 @@ def get_type_headers(filename, data):
     mimetype, encoding = guess_type(filename, data)
     if not mimetype:
         return None
-    headers = {'X-Content-Type-Options': 'nosniff'}
+    headers = {str('X-Content-Type-Options'): 'nosniff'}
     if 'html' in mimetype or 'javascript' in mimetype or 'svg' in mimetype:
         mimetype = 'application/octet-stream'
-        headers['Content-Disposition'] = 'attachment'
+        headers[str('Content-Disposition')] = 'attachment'
     if encoding:
         mimetype += '; charset={encoding}'.format(encoding=encoding)
-    headers['Content-Type'] = mimetype
+    headers[str('Content-Type')] = mimetype
     return headers
diff --git a/pagure/ui/repo.py b/pagure/ui/repo.py
index 4a6cfd7..325f8ed 100644
--- a/pagure/ui/repo.py
+++ b/pagure/ui/repo.py
@@ -596,7 +596,7 @@ def view_file(repo, identifier, filename, username=None, namespace=None):
         output_type = 'tree'
 
     if output_type == 'binary':
-        headers['Content-Disposition'] = 'attachment'
+        headers[str('Content-Disposition')] = 'attachment'
 
     return flask.Response(flask.stream_with_context(
         stream_template(