diff --git a/lib/ldapauth.js b/lib/ldapauth.js
index b825fc0..e356a57 100644
--- a/lib/ldapauth.js
+++ b/lib/ldapauth.js
@@ -283,6 +283,10 @@ LdapAuth.prototype._findUser = function (username, callback) {
         return callback(new Error("LDAP connection is not yet bound"));
     }
 
+    if(self.opts.searchFilter.indexOf('{{username}}') === -1){
+        return callback(new Error("missing pattern for username in searchFilter"));
+    }
+    
     var searchFilter = self.opts.searchFilter.replace('{{username}}', username);
     var opts = {
         filter: searchFilter,