diff --git a/plugins/Owner/plugin.py b/plugins/Owner/plugin.py
index eb7e95e27..6da42b832 100644
--- a/plugins/Owner/plugin.py
+++ b/plugins/Owner/plugin.py
@@ -192,7 +192,8 @@ class Owner(callbacks.Plugin):
             conf.registerNetwork(network, password)
             serverS = '%s:%s' % serverPort
             conf.supybot.networks.get(network).servers.append(serverS)
-            assert conf.supybot.networks.get(network).servers()
+            assert conf.supybot.networks.get(network).servers(), \
+                   'No servers are set for the %s network.' % network
         self.log.info('Creating new Irc for %s.', network)
         newIrc = irclib.Irc(network)
         for irc in world.ircs:
diff --git a/src/plugin.py b/src/plugin.py
index ff5d43bf2..5c35d7daa 100644
--- a/src/plugin.py
+++ b/src/plugin.py
@@ -101,7 +101,8 @@ def loadPluginClass(irc, module, register=None):
     if hasattr(cb, 'public'):
         public = cb.public
     conf.registerPlugin(plugin, register, public)
-    assert not irc.getCallback(plugin)
+    assert not irc.getCallback(plugin), \
+           'There is already a %r plugin registered.' % plugin
     try:
         renames = []#XXX registerRename(plugin)()
         if renames: