diff --git a/lib/ldapauth.js b/lib/ldapauth.js
index 63c5d1e..5462ffe 100644
--- a/lib/ldapauth.js
+++ b/lib/ldapauth.js
@@ -13,7 +13,6 @@
  */
 
 var assert = require('assert');
-var bcrypt = require('bcrypt');
 var ldap = require('ldapjs');
 var debug = console.warn;
 var format = require('util').format;
@@ -53,7 +52,6 @@ var format = require('util').format;
 function LdapAuth(opts) {
   this.opts = opts;
   assert.ok(opts.url);
-  assert.ok(opts.adminDn);
   assert.ok(opts.searchBase);
   assert.ok(opts.searchFilter);
 
@@ -81,7 +79,10 @@ function LdapAuth(opts) {
   this._adminBound = false;
   this._userClient = ldap.createClient(clientOpts);
 
-  this._salt = bcrypt.genSaltSync();
+  if (opts.cache) {
+    var bcrypt = require('bcrypt');
+    this._salt = bcrypt.genSaltSync();
+  }
 }
 
 
@@ -180,6 +181,7 @@ LdapAuth.prototype.authenticate = function (username, password, callback) {
   if (self.opts.cache) {
     // Check cache. 'cached' is `{password: <hashed-password>, user: <user>}`.
     var cached = self.userCache.get(username);
+    var bcrypt = require('bcrypt');
     if (cached && bcrypt.compareSync(password, cached.password)) {
       return callback(null, cached.user)
     }
@@ -198,6 +200,7 @@ LdapAuth.prototype.authenticate = function (username, password, callback) {
         return callback(err);
       }
       if (self.opts.cache) {
+        var bcrypt = require('bcrypt');
         bcrypt.hash(password, self._salt, function (err, hash) {
           self.userCache.set(username, {password: hash, user: user});
           return callback(null, user);
diff --git a/package.json b/package.json
index e419a1d..3866e64 100644
--- a/package.json
+++ b/package.json
@@ -16,7 +16,9 @@
   "engines": ["node >=0.8.0"],
   "dependencies": {
     "ldapjs": "0.6.3",
-    "bcrypt": "0.7.5",
     "lru-cache": "2.0.4"
+  },
+  "optionalDependencies": {
+    "bcrypt": "0.7.5"
   }
 }