diff --git a/src/Orchard.Tests.Modules/Users/Services/UserServiceTests.cs b/src/Orchard.Tests.Modules/Users/Services/UserServiceTests.cs
index eb2a0e57f..22b00929e 100644
--- a/src/Orchard.Tests.Modules/Users/Services/UserServiceTests.cs
+++ b/src/Orchard.Tests.Modules/Users/Services/UserServiceTests.cs
@@ -1,6 +1,4 @@
 using System;
-using System.Globalization;
-using System.Threading;
 using System.Xml.Linq;
 using Autofac;
 using Moq;
@@ -124,18 +122,5 @@ namespace Orchard.Tests.Modules.Users.Services {
             Assert.That(username, Is.EqualTo("foo"));
             Assert.That(validateByUtc, Is.GreaterThan(_clock.UtcNow));
         }
-
-        [Test]
-        public void VerifyUserUnicityTurkishTest() {
-            CultureInfo turkishCulture = new CultureInfo("tr-TR");
-            Thread.CurrentThread.CurrentCulture = turkishCulture;
-
-            // Create user lower case
-            _membershipService.CreateUser(new CreateUserParams("admin", "66554321", "foo@bar.com", "", "", true));
-            _container.Resolve<IOrchardServices>().ContentManager.Flush();
-
-            // Verify unicity with upper case which with turkish coallition would yeld admin with an i without the dot and therefore generate a different user name
-            Assert.That(_userService.VerifyUserUnicity("ADMIN", "differentfoo@bar.com"), Is.False); // should fail
-        }
     }
 }
diff --git a/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs b/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs
index 33df35610..b83896b2e 100644
--- a/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs
+++ b/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs
@@ -245,7 +245,7 @@ namespace Orchard.Users.Controllers {
                         _siteService.GetSiteSettings().As<SiteSettingsPart>().SuperUser = editModel.UserName;
                     }
 
-                    user.NormalizedUserName = editModel.UserName.ToUpperInvariant();
+                    user.NormalizedUserName = editModel.UserName.ToLower();
                 }
             }
 
diff --git a/src/Orchard.Web/Modules/Orchard.Users/Migrations.cs b/src/Orchard.Web/Modules/Orchard.Users/Migrations.cs
index 7b041f320..4175a2dc5 100644
--- a/src/Orchard.Web/Modules/Orchard.Users/Migrations.cs
+++ b/src/Orchard.Web/Modules/Orchard.Users/Migrations.cs
@@ -1,24 +1,15 @@
-using System.Collections.Generic;
-using Orchard.ContentManagement;
-using Orchard.Data.Migration;
-using Orchard.Users.Models;
+using Orchard.Data.Migration;
 
 namespace Orchard.Users {
     public class UsersDataMigration : DataMigrationImpl {
 
-        public UsersDataMigration(IOrchardServices orchardServices) {
-            Services = orchardServices;
-        }
-
-        public IOrchardServices Services { get; set; }
-
         public int Create() {
             SchemaBuilder.CreateTable("UserPartRecord", 
                 table => table
                     .ContentPartRecord()
                     .Column<string>("UserName")
                     .Column<string>("Email")
-                    .Column<string>("NormalizedUserName", c => c.Unique())
+                    .Column<string>("NormalizedUserName")
                     .Column<string>("Password")
                     .Column<string>("PasswordFormat")
                     .Column<string>("HashAlgorithm")
@@ -41,17 +32,7 @@ namespace Orchard.Users {
                     .Column<bool>("EnableLostPassword", c => c.WithDefault(false))
                 );
 
-            return 2;
-        }
-
-        public int UpdateFrom1() {
-            IEnumerable<UserPart> users = Services.ContentManager.Query<UserPart, UserPartRecord>().List();
-
-            foreach (UserPart user in users) {
-                user.NormalizedUserName = user.UserName.ToUpperInvariant();
-            }
-
-            return 2;
+            return 1;
         }
     }
 }
\ No newline at end of file
diff --git a/src/Orchard.Web/Modules/Orchard.Users/Services/MembershipService.cs b/src/Orchard.Web/Modules/Orchard.Users/Services/MembershipService.cs
index 44936191a..163685cc1 100644
--- a/src/Orchard.Web/Modules/Orchard.Users/Services/MembershipService.cs
+++ b/src/Orchard.Web/Modules/Orchard.Users/Services/MembershipService.cs
@@ -49,7 +49,7 @@ namespace Orchard.Users.Services {
 
             user.Record.UserName = createUserParams.Username;
             user.Record.Email = createUserParams.Email;
-            user.Record.NormalizedUserName = createUserParams.Username.ToUpperInvariant();
+            user.Record.NormalizedUserName = createUserParams.Username.ToLower();
             user.Record.HashAlgorithm = "SHA1";
             SetPassword(user.Record, createUserParams.Password);
 
@@ -97,24 +97,18 @@ namespace Orchard.Users.Services {
         }
 
         public IUser GetUser(string username) {
-            var higherName = username == null ? "" : username.ToUpperInvariant();
+            var lowerName = username == null ? "" : username.ToLower();
 
-            return _orchardServices.ContentManager.Query<UserPart, UserPartRecord>()
-                .Where(u => u.NormalizedUserName == higherName).List()
-                .FirstOrDefault(u => u.UserName.Equals(username, StringComparison.OrdinalIgnoreCase));
+            return _orchardServices.ContentManager.Query<UserPart, UserPartRecord>().Where(u => u.NormalizedUserName == lowerName).List().FirstOrDefault();
         }
 
         public IUser ValidateUser(string userNameOrEmail, string password) {
-            var higherName = userNameOrEmail == null ? "" : userNameOrEmail.ToUpperInvariant();
+            var lowerName = userNameOrEmail == null ? "" : userNameOrEmail.ToLower();
 
-            var user = _orchardServices.ContentManager.Query<UserPart, UserPartRecord>()
-                .Where(u =>
-                       u.NormalizedUserName == higherName ||
-                       u.Email == userNameOrEmail)
-                .List()
-                .FirstOrDefault(u =>
-                                u.UserName.Equals(userNameOrEmail, StringComparison.OrdinalIgnoreCase) ||
-                                u.Email == userNameOrEmail);
+            var user = _orchardServices.ContentManager.Query<UserPart, UserPartRecord>().Where(u => u.NormalizedUserName == lowerName).List().FirstOrDefault();
+
+            if (user == null)
+                user = _orchardServices.ContentManager.Query<UserPart, UserPartRecord>().Where(u => u.Email == lowerName).List().FirstOrDefault();
 
             if ( user == null || ValidatePassword(user.As<UserPart>().Record, password) == false )
                 return null;
diff --git a/src/Orchard.Web/Modules/Orchard.Users/Services/UserService.cs b/src/Orchard.Web/Modules/Orchard.Users/Services/UserService.cs
index 90ad4cf19..6b84fb063 100644
--- a/src/Orchard.Web/Modules/Orchard.Users/Services/UserService.cs
+++ b/src/Orchard.Web/Modules/Orchard.Users/Services/UserService.cs
@@ -37,16 +37,13 @@ namespace Orchard.Users.Services {
         public ILogger Logger { get; set; }
 
         public bool VerifyUserUnicity(string userName, string email) {
-            string normalizedUserName = userName.ToUpperInvariant();
+            string normalizedUserName = userName.ToLower();
 
             if (_contentManager.Query<UserPart, UserPartRecord>()
                                    .Where(user => 
                                           user.NormalizedUserName == normalizedUserName || 
                                           user.Email == email)
-                                   .List()
-                                   .Any(user =>
-                                          user.UserName.Equals(userName, StringComparison.OrdinalIgnoreCase) ||
-                                          user.Email == email)) {
+                                   .List().Any()) {
                 return false;
             }
 
@@ -54,17 +51,13 @@ namespace Orchard.Users.Services {
         }
 
         public bool VerifyUserUnicity(int id, string userName, string email) {
-            string normalizedUserName = userName.ToUpperInvariant();
+            string normalizedUserName = userName.ToLower();
 
             if (_contentManager.Query<UserPart, UserPartRecord>()
                                    .Where(user =>
                                           user.NormalizedUserName == normalizedUserName ||
                                           user.Email == email)
-                                   .List()
-                                   .Any(user =>
-                                          (user.UserName.Equals(userName, StringComparison.OrdinalIgnoreCase) ||
-                                          user.Email == email) &&
-                                          user.Id != id)) {
+                                   .List().Any(user => user.Id != id)) {
                 return false;
             }