diff --git a/src/Umbraco.Core/Persistence/Repositories/MemberGroupRepository.cs b/src/Umbraco.Core/Persistence/Repositories/MemberGroupRepository.cs
index 4b9d39c99c..e0997967bc 100644
--- a/src/Umbraco.Core/Persistence/Repositories/MemberGroupRepository.cs
+++ b/src/Umbraco.Core/Persistence/Repositories/MemberGroupRepository.cs
@@ -201,12 +201,13 @@ namespace Umbraco.Core.Persistence.Repositories
             //find the member by username
             var memberSql = new Sql();
             var memberObjectType = new Guid(Constants.ObjectTypes.Member);
+            var escapedUsername = PetaPocoExtensions.EscapeAtSymbols(username);
             memberSql.Select("umbracoNode.id")
                 .From<NodeDto>()
                 .InnerJoin<MemberDto>()
                 .On<NodeDto, MemberDto>(dto => dto.NodeId, dto => dto.NodeId)
                 .Where<NodeDto>(x => x.NodeObjectType == memberObjectType)
-                .Where<MemberDto>(x => x.LoginName == username);
+                .Where<MemberDto>(x => x.LoginName == escapedUsername);
             var memberIdUsername = Database.Fetch<int?>(memberSql).FirstOrDefault();
             if (memberIdUsername.HasValue == false)
             {
diff --git a/src/Umbraco.Tests/Services/MemberServiceTests.cs b/src/Umbraco.Tests/Services/MemberServiceTests.cs
index 108c8f4bf8..9c70047b20 100644
--- a/src/Umbraco.Tests/Services/MemberServiceTests.cs
+++ b/src/Umbraco.Tests/Services/MemberServiceTests.cs
@@ -205,6 +205,25 @@ namespace Umbraco.Tests.Services
             Assert.AreEqual(2, membersInRole.Count());
         }
 
+        [Test]
+        public void Associate_Members_To_Roles_With_Member_Username_Containing_At_Symbols()
+        {
+            ServiceContext.MemberService.AddRole("MyTestRole1");
+
+            IMemberType memberType = MockedContentTypes.CreateSimpleMemberType();
+            ServiceContext.MemberTypeService.Save(memberType);
+            var member1 = MockedMember.CreateSimpleMember(memberType, "test1", "test1@test.com", "pass", "test1@test.com");
+            ServiceContext.MemberService.Save(member1);
+            var member2 = MockedMember.CreateSimpleMember(memberType, "test2", "test2@test.com", "pass", "test2@test.com");
+            ServiceContext.MemberService.Save(member2);
+
+            ServiceContext.MemberService.AssignRoles(new[] { member1.Username, member2.Username }, new[] { "MyTestRole1" });
+
+            var membersInRole = ServiceContext.MemberService.GetMembersInRole("MyTestRole1");
+
+            Assert.AreEqual(2, membersInRole.Count());
+        }
+
         [Test]
         public void Associate_Members_To_Roles_With_New_Role()
         {
diff --git a/src/Umbraco.Web/Security/Providers/MembersRoleProvider.cs b/src/Umbraco.Web/Security/Providers/MembersRoleProvider.cs
index 274c2eab99..2ddbc0b5a2 100644
--- a/src/Umbraco.Web/Security/Providers/MembersRoleProvider.cs
+++ b/src/Umbraco.Web/Security/Providers/MembersRoleProvider.cs
@@ -1,3 +1,5 @@
+using System.Collections.Specialized;
+using System.Configuration.Provider;
 using System.Linq;
 using System.Web.Security;
 using Umbraco.Core;
@@ -22,7 +24,7 @@ namespace Umbraco.Web.Security.Providers
         }
 
         private string _applicationName;
-
+        
         public override bool IsUserInRole(string username, string roleName)
         {
             return GetRolesForUser(username).Any(x => x == roleName);
@@ -73,10 +75,27 @@ namespace Umbraco.Web.Security.Providers
             return _roleService.FindMembersInRole(roleName, usernameToMatch, StringPropertyMatchType.Wildcard).Select(x => x.Username).ToArray();
         }
 
+        /// <summary>
+        /// The name of the application using the custom role provider.
+        /// </summary>
+        /// <value></value>
+        /// <returns>The name of the application using the custom membership provider.</returns>
         public override string ApplicationName
         {
-            get { return _applicationName; }
-            set { _applicationName = value; }
+            get
+            {
+                return _applicationName;
+            }
+            set
+            {
+                if (string.IsNullOrEmpty(value))
+                    throw new ProviderException("ApplicationName cannot be empty.");
+
+                if (value.Length > 0x100)
+                    throw new ProviderException("Provider application name too long.");
+
+                _applicationName = value;
+            }
         }
     }
 }
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