diff --git a/gns3server/controller/compute.py b/gns3server/controller/compute.py
index 3d6822c8..6a4ac0ce 100644
--- a/gns3server/controller/compute.py
+++ b/gns3server/controller/compute.py
@@ -529,7 +529,7 @@ class Compute:
                 raise aiohttp.web.HTTPForbidden(text=msg)
             elif response.status == 404:
                 raise aiohttp.web.HTTPNotFound(text="{} {} not found".format(method, path))
-            elif response.status == 408:
+            elif response.status == 408 or response.status == 504:
                 raise aiohttp.web.HTTPRequestTimeout(text="{} {} request timeout".format(method, path))
             elif response.status == 409:
                 try:
diff --git a/gns3server/web/web_server.py b/gns3server/web/web_server.py
index 1e8bd1b8..0bcc71a5 100644
--- a/gns3server/web/web_server.py
+++ b/gns3server/web/web_server.py
@@ -33,6 +33,7 @@ from .route import Route
 from ..config import Config
 from ..compute import MODULES
 from ..compute.port_manager import PortManager
+from ..compute.qemu import Qemu
 from ..controller import Controller
 
 
@@ -192,6 +193,10 @@ class WebServer:
         Called when the HTTP server start
         """
         yield from Controller.instance().start()
+        # Because with a large image collection
+        # without md5sum already computed we start the
+        # computing with server start
+        asyncio.async(Qemu.instance().list_images())
 
     def run(self):
         """