diff --git a/MediaBrowser.Api/UserService.cs b/MediaBrowser.Api/UserService.cs
index 1a12c54390..1e928c301e 100644
--- a/MediaBrowser.Api/UserService.cs
+++ b/MediaBrowser.Api/UserService.cs
@@ -281,6 +281,11 @@ namespace MediaBrowser.Api
         {
             var user = _userManager.Users.FirstOrDefault(i => string.Equals(request.Username, i.Name, StringComparison.OrdinalIgnoreCase));
 
+            if (user == null)
+            {
+                throw new ArgumentException(string.Format("User {0} not found.", request.Username));
+            }
+
             var result = AuthenticateUser(new AuthenticateUser { Id = user.Id, Password = request.Password }).Result;
 
             return ToOptimizedResult(result);
diff --git a/MediaBrowser.WebDashboard/packages.config b/MediaBrowser.WebDashboard/packages.config
index 984899a0a1..8b53d9d782 100644
--- a/MediaBrowser.WebDashboard/packages.config
+++ b/MediaBrowser.WebDashboard/packages.config
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="MediaBrowser.ApiClient.Javascript" version="3.0.153" targetFramework="net45" />
+  <package id="MediaBrowser.ApiClient.Javascript" version="3.0.155" targetFramework="net45" />
   <package id="ServiceStack.Common" version="3.9.56" targetFramework="net45" />
   <package id="ServiceStack.Text" version="3.9.55" targetFramework="net45" />
 </packages>
\ No newline at end of file