diff --git a/lib/authorizer.js b/lib/authorizer.js
index 067cb01..d33e181 100644
--- a/lib/authorizer.js
+++ b/lib/authorizer.js
@@ -88,11 +88,13 @@ Authorizer.prototype._authenticate = function(client, user, pass, cb) {
     return;
   }
 
+  user = user.toString();
+
   client.user = user;
   user = this.users[user];
 
   hasher({
-    password: pass,
+    password: pass.toString(),
     salt: user.salt
   }, function(err, pass, salt, hash) {
     if (err) {
@@ -132,7 +134,7 @@ Authorizer.prototype.addUser = function(user, pass, authorizePublish,
   }
 
   hasher({
-    password: pass
+    password: pass.toString()
   }, function(err, pass, salt, hash) {
     if (!err) {
       that.users[user] = {
diff --git a/package.json b/package.json
index e638743..9ebf587 100644
--- a/package.json
+++ b/package.json
@@ -64,7 +64,7 @@
     "mongo-clean": "0.0.1"
   },
   "dependencies": {
-    "mqtt": "~0.3.8",
+    "mqtt": "~0.3.9",
     "async": "~0.7.0",
     "ascoltatori": "~0.15.0",
     "commander": "~2.2.0",
diff --git a/test/abstract_server.js b/test/abstract_server.js
index ce43ac6..eac66fb 100644
--- a/test/abstract_server.js
+++ b/test/abstract_server.js
@@ -976,8 +976,8 @@ module.exports = function(moscaSettings, createConnection) {
 
   it("should support authentication (success)", function(done) {
     instance.authenticate = function(client, username, password, callback) {
-      expect(username).to.be.eql("matteo");
-      expect(password).to.be.eql("collina");
+      expect(username.toString()).to.be.eql("matteo");
+      expect(password.toString()).to.be.eql("collina");
       callback(null, true);
     };
 
@@ -998,8 +998,8 @@ module.exports = function(moscaSettings, createConnection) {
 
   it("should support authentication (failure)", function(done) {
     instance.authenticate = function(client, username, password, callback) {
-      expect(username).to.be.eql("matteo");
-      expect(password).to.be.eql("collina");
+      expect(username.toString()).to.be.eql("matteo");
+      expect(password.toString()).to.be.eql("collina");
       callback(null, false);
     };