diff --git a/Lib/BaseHTTPServer.py b/Lib/BaseHTTPServer.py
index 4d6d058..cbc60e4 100644
--- a/Lib/BaseHTTPServer.py
+++ b/Lib/BaseHTTPServer.py
@@ -287,6 +287,7 @@
         explain = long
         self.log_error("code %d, message %s", code, message)
         self.send_response(code, message)
+        self.send_header("Content-Type", "text/html")
         self.end_headers()
         self.wfile.write(self.error_message_format %
                          {'code': code,