diff --git a/src/Microsoft.AspNet.Identity/IdentityBuilder.cs b/src/Microsoft.AspNet.Identity/IdentityBuilder.cs
index 259fc42a95..a6214cce5b 100644
--- a/src/Microsoft.AspNet.Identity/IdentityBuilder.cs
+++ b/src/Microsoft.AspNet.Identity/IdentityBuilder.cs
@@ -16,9 +16,10 @@ namespace Microsoft.AspNet.Identity
             Services = services;
         }
 
-        public IdentityBuilder<TUser, TRole> AddInstance<T>(T obj)
+        public IdentityBuilder<TUser, TRole> AddInstance<TService>(TService instance)
+            where TService : class
         {
-            Services.AddInstance(obj);
+            Services.AddInstance(instance);
             return this;
         }
 
diff --git a/test/Microsoft.AspNet.Identity.Test/IdentityBuilderTest.cs b/test/Microsoft.AspNet.Identity.Test/IdentityBuilderTest.cs
index dcea443aea..5ce7b7ce57 100644
--- a/test/Microsoft.AspNet.Identity.Test/IdentityBuilderTest.cs
+++ b/test/Microsoft.AspNet.Identity.Test/IdentityBuilderTest.cs
@@ -52,6 +52,7 @@ namespace Microsoft.AspNet.Identity.Test
         }
 
         private static void CanOverride<TService>(TService instance)
+            where TService : class
         {
             var services = new ServiceCollection();
             services.AddIdentity<IdentityUser>().AddInstance(instance);