diff --git a/tools/httpd_sim.py b/tools/httpd_sim.py
index 9105da8b..b589c0c8 100755
--- a/tools/httpd_sim.py
+++ b/tools/httpd_sim.py
@@ -304,8 +304,9 @@ class Handler(SimpleHTTPRequestHandler):
             pieces = cmd.split(" ")
             handler = self.get_parsers().get(pieces[0])
             result = handler(pieces)
-            response.extend(result)
-            response.extend(b"\n")
+            if(result is not None):
+                response.extend(result)
+                response.extend(b"\n")
         return response
 
     def get_parsers(self):