diff --git a/visualisation/visualisation.py b/visualisation/visualisation.py
index e1b000b..e73c860 100644
--- a/visualisation/visualisation.py
+++ b/visualisation/visualisation.py
@@ -22,7 +22,7 @@
 #  graphics on demand.
 #
 
-import os, sys, logging, time, datetime, re
+import os, sys, logging, time, datetime, re, signal
 from multiprocessing import Process
 from BaseHTTPServer import BaseHTTPRequestHandler
 from BaseHTTPServer import HTTPServer
@@ -67,12 +67,14 @@
         self.p = Process(target=self.visloop, args=())
         self.p.start()
 
+    def _receive_signal(self, signum, stack):
+        if signum == signal.SIGUSR1:
+            self.state.db_ok = True
+
     # The main loop for the visualisation webserver
     def visloop(self):
+        self.state.db_ok = False
         self.state.cache = GraphicsCache()
-        self.state.db = VlanDB(db_name=self.state.config.database.dbname,
-                               username=self.state.config.database.username,
-                               readonly=True)
 
         loglevel = VlanUtil().set_logging_level(self.state.config.logging.level)
 
@@ -88,6 +90,18 @@
                                 filemode = 'a')
             logging.info('%s visualisation starting up', self.state.banner)
 
+        # Wait for main process to signal to us that it's finished with any
+        # database upgrades and we can open it without any problems.
+        signal.signal(signal.SIGUSR1, self._receive_signal)
+        while not self.state.db_ok:
+            logging.info('%s visualisation waiting for db_ok signal', self.state.banner)
+            time.sleep(1)
+        logging.info('%s visualisation received db_ok signal', self.state.banner)
+
+        self.state.db = VlanDB(db_name=self.state.config.database.dbname,
+                               username=self.state.config.database.username,
+                               readonly=True)
+
         server = VlandHTTPServer(('', self.state.config.visualisation.port),
                                  GetHandler, self.state)
         server.serve_forever()
@@ -96,6 +110,10 @@
     def shutdown(self):
         self.p.terminate()
 
+    # Kill the webserver
+    def signal_db_ok(self):
+        os.kill(self.p.pid, signal.SIGUSR1)
+
 class GetHandler(BaseHTTPRequestHandler):
     """ Methods to generate and serve the pages """