diff --git a/confluent_server/confluent/httpapi.py b/confluent_server/confluent/httpapi.py
index c66f8f32..037fd1d4 100644
--- a/confluent_server/confluent/httpapi.py
+++ b/confluent_server/confluent/httpapi.py
@@ -264,7 +264,7 @@ def _pick_mimetype(env):
         return 'application/json; charset=utf-8', '.json'
     elif env['PATH_INFO'].endswith('.html'):
         return 'text/html', '.html'
-    elif 'application/json' in env['HTTP_ACCEPT']:
+    elif 'HTTP_ACCEPT' in env and 'application/json' in env['HTTP_ACCEPT']:
         return 'application/json; charset=utf-8', ''
     else:
         return 'text/html', ''