diff --git a/lib/web/auth/ldap/index.js b/lib/web/auth/ldap/index.js
index 1a5c993..6aa9789 100644
--- a/lib/web/auth/ldap/index.js
+++ b/lib/web/auth/ldap/index.js
@@ -23,11 +23,18 @@ passport.use(new LDAPStrategy({
     tlsOptions: config.ldap.tlsOptions || null
   }
 }, function (user, done) {
-  var uuid = user.uidNumber || user.uid || user.sAMAccountName
+  var uuid = user.uidNumber || user.uid || user.sAMAccountName || undefined
   if (config.ldap.useridField && user[config.ldap.useridField]) {
     uuid = user[config.ldap.useridField]
   }
 
+  if (typeof uuid === 'undefined') {
+    throw new Error('Could not determine UUID for LDAP user. Check that ' +
+    'either uidNumber, uid or sAMAccountName is set in your LDAP directory ' +
+    'or use another unique attribute and configure it using the ' +
+    '"useridField" option in ldap settings.')
+  }
+
   var username = uuid
   if (config.ldap.usernameField && user[config.ldap.usernameField]) {
     username = user[config.ldap.usernameField]