diff --git a/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs b/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs
index 1e29bedfa..82a18d230 100644
--- a/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs
+++ b/src/Orchard.Web/Modules/Orchard.Users/Controllers/AdminController.cs
@@ -74,7 +74,7 @@ namespace Orchard.Users.Controllers {
                     break;
             }
 
-            if(!String.IsNullOrWhiteSpace(options.Search)) {
+            if(!string.IsNullOrWhiteSpace(options.Search)) {
                 users = users.Where(u => u.UserName.Contains(options.Search) || u.Email.Contains(options.Search));
             }
 
@@ -219,6 +219,10 @@ namespace Orchard.Users.Controllers {
                 return new HttpUnauthorizedResult();
 
             var user = Services.ContentManager.Get<UserPart>(id);
+
+            if (user == null)
+                return HttpNotFound();
+
             var editor = Shape.EditorTemplate(TemplateName: "Parts/User.Edit", Model: new UserEditViewModel {User = user}, Prefix: null);
             editor.Metadata.Position = "2";
             var model = Services.ContentManager.BuildEditor(user);
@@ -233,11 +237,15 @@ namespace Orchard.Users.Controllers {
                 return new HttpUnauthorizedResult();
 
             var user = Services.ContentManager.Get<UserPart>(id, VersionOptions.DraftRequired);
+
+            if (user == null)
+                return HttpNotFound();
+
             string previousName = user.UserName;
 
             var model = Services.ContentManager.UpdateEditor(user, this);
 
-            var editModel = new UserEditViewModel {User = user};
+            var editModel = new UserEditViewModel { User = user };
             if (TryUpdateModel(editModel)) {
                 if (!_userService.VerifyUserUnicity(id, editModel.UserName, editModel.Email)) {
                     AddModelError("NotUniqueUserName", T("User with that username and/or email already exists."));
@@ -248,7 +256,7 @@ namespace Orchard.Users.Controllers {
                 }
                 else {
                     // also update the Super user if this is the renamed account
-                    if (String.Equals(Services.WorkContext.CurrentSite.SuperUser, previousName, StringComparison.Ordinal)) {
+                    if (string.Equals(Services.WorkContext.CurrentSite.SuperUser, previousName, StringComparison.Ordinal)) {
                         _siteService.GetSiteSettings().As<SiteSettingsPart>().SuperUser = editModel.UserName;
                     }
 
@@ -279,17 +287,18 @@ namespace Orchard.Users.Controllers {
 
             var user = Services.ContentManager.Get<IUser>(id);
 
-            if (user != null) {
-                if (String.Equals(Services.WorkContext.CurrentSite.SuperUser, user.UserName, StringComparison.Ordinal)) {
-                    Services.Notifier.Error(T("The Super user can't be removed. Please disable this account or specify another Super user account."));
-                }
-                else if (String.Equals(Services.WorkContext.CurrentUser.UserName, user.UserName, StringComparison.Ordinal)) {
-                    Services.Notifier.Error(T("You can't remove your own account. Please log in with another account."));
-                }
-                else{
-                    Services.ContentManager.Remove(user.ContentItem);
-                    Services.Notifier.Information(T("User {0} deleted", user.UserName));
-                }
+            if (user == null)
+                return HttpNotFound();
+
+            if (string.Equals(Services.WorkContext.CurrentSite.SuperUser, user.UserName, StringComparison.Ordinal)) {
+                Services.Notifier.Error(T("The Super user can't be removed. Please disable this account or specify another Super user account."));
+            }
+            else if (string.Equals(Services.WorkContext.CurrentUser.UserName, user.UserName, StringComparison.Ordinal)) {
+                Services.Notifier.Error(T("You can't remove your own account. Please log in with another account."));
+            }
+            else {
+                Services.ContentManager.Remove(user.ContentItem);
+                Services.Notifier.Information(T("User {0} deleted", user.UserName));
             }
 
             return RedirectToAction("Index");
@@ -302,16 +311,18 @@ namespace Orchard.Users.Controllers {
 
             var user = Services.ContentManager.Get<IUser>(id);
 
-            if ( user != null ) {
-                var siteUrl = Services.WorkContext.CurrentSite.BaseUrl;
-                if (String.IsNullOrWhiteSpace(siteUrl)) {
-                    siteUrl = HttpContext.Request.ToRootUrlString();
-                }
+            if (user == null)
+                return HttpNotFound();
 
-                _userService.SendChallengeEmail(user.As<UserPart>(), nonce => Url.MakeAbsolute(Url.Action("ChallengeEmail", "Account", new { Area = "Orchard.Users", nonce = nonce }), siteUrl));
-                Services.Notifier.Information(T("Challenge email sent to {0}", user.UserName));
+            var siteUrl = Services.WorkContext.CurrentSite.BaseUrl;
+
+            if (string.IsNullOrWhiteSpace(siteUrl)) {
+                siteUrl = HttpContext.Request.ToRootUrlString();
             }
 
+            _userService.SendChallengeEmail(user.As<UserPart>(), nonce => Url.MakeAbsolute(Url.Action("ChallengeEmail", "Account", new { Area = "Orchard.Users", nonce = nonce }), siteUrl));
+            Services.Notifier.Information(T("Challenge email sent to {0}", user.UserName));
+
 
             return RedirectToAction("Index");
         }
@@ -323,11 +334,12 @@ namespace Orchard.Users.Controllers {
 
             var user = Services.ContentManager.Get<IUser>(id);
 
-            if ( user != null ) {
-                user.As<UserPart>().RegistrationStatus = UserStatus.Approved;
-                Services.Notifier.Information(T("User {0} approved", user.UserName));
-                _userEventHandlers.Approved(user);
-            }
+            if (user == null)
+                return HttpNotFound();
+
+            user.As<UserPart>().RegistrationStatus = UserStatus.Approved;
+            Services.Notifier.Information(T("User {0} approved", user.UserName));
+            _userEventHandlers.Approved(user);
 
             return RedirectToAction("Index");
         }
@@ -339,14 +351,15 @@ namespace Orchard.Users.Controllers {
 
             var user = Services.ContentManager.Get<IUser>(id);
 
-            if (user != null) {
-                if (String.Equals(Services.WorkContext.CurrentUser.UserName, user.UserName, StringComparison.Ordinal)) {
-                    Services.Notifier.Error(T("You can't disable your own account. Please log in with another account"));
-                }
-                else {
-                    user.As<UserPart>().RegistrationStatus = UserStatus.Pending;
-                    Services.Notifier.Information(T("User {0} disabled", user.UserName));
-                }
+            if (user == null)
+                return HttpNotFound();
+
+            if (string.Equals(Services.WorkContext.CurrentUser.UserName, user.UserName, StringComparison.Ordinal)) {
+                Services.Notifier.Error(T("You can't disable your own account. Please log in with another account"));
+            }
+            else {
+                user.As<UserPart>().RegistrationStatus = UserStatus.Pending;
+                Services.Notifier.Information(T("User {0} disabled", user.UserName));
             }
 
             return RedirectToAction("Index");