diff --git a/plugins/NickAuth/plugin.py b/plugins/NickAuth/plugin.py
index d2bbabd5b..ab8dada76 100644
--- a/plugins/NickAuth/plugin.py
+++ b/plugins/NickAuth/plugin.py
@@ -161,7 +161,12 @@ class NickAuth(callbacks.Plugin):
         if not user:
             user = ircdb.users.getUserFromNick(irc.network, theirnick)
         if user:
-            user.addAuth(prefix)
+            try:
+                user.addAuth(prefix)
+            except ValueError:
+                irc.error(_('Your secure flag is true and your hostmask '
+                          'doesn\'t match any of your known hostmasks.'),
+                          Raise=True)
             ircdb.users.setUser(user, flush=False)
             irc.reply(_('You are now authenticated as %s.') % user.name)
         else:
diff --git a/plugins/User/plugin.py b/plugins/User/plugin.py
index 5978026eb..f18f1440b 100644
--- a/plugins/User/plugin.py
+++ b/plugins/User/plugin.py
@@ -522,7 +522,12 @@ class User(callbacks.Plugin):
                 found = False
                 for (id, user) in ircdb.users.items():
                     if keyid in [x[-len(keyid):] for x in user.gpgkeys]:
-                        user.addAuth(msg.prefix)
+                        try:
+                            user.addAuth(msg.prefix)
+                        except ValueError:
+                            irc.error(_('Your secure flag is true and your '
+                                      'hostmask doesn\'t match any of your '
+                                      'known hostmasks.'), Raise=True)
                         ircdb.users.setUser(user, flush=False)
                         irc.reply(_('You are now authenticated as %s.') %
                                 user.name)