diff --git a/src/Microsoft.AspNet.Identity/UserManager.cs b/src/Microsoft.AspNet.Identity/UserManager.cs
index a40f1213ed..5456ad98a9 100644
--- a/src/Microsoft.AspNet.Identity/UserManager.cs
+++ b/src/Microsoft.AspNet.Identity/UserManager.cs
@@ -205,7 +205,6 @@ namespace Microsoft.AspNet.Identity
         /// true if the backing user store supports user emails, otherwise false.
         /// </value>
         public virtual bool SupportsUserEmail 
-
         {
             get
             {
@@ -1032,8 +1031,7 @@ namespace Microsoft.AspNet.Identity
                 throw new ArgumentNullException("user");
             }
 
-            var userRoles = await userRoleStore.GetRolesAsync(user, CancellationToken);
-            if (userRoles.Contains(role))
+            if (await userRoleStore.IsInRoleAsync(user, role, CancellationToken))
             {
                 return await UserAlreadyInRoleError(user, role);
             }
@@ -1063,10 +1061,9 @@ namespace Microsoft.AspNet.Identity
                 throw new ArgumentNullException("roles");
             }
 
-            var userRoles = await userRoleStore.GetRolesAsync(user, CancellationToken);
-            foreach (var role in roles)
+            foreach (var role in roles.Distinct())
             {
-                if (userRoles.Contains(role))
+                if (await userRoleStore.IsInRoleAsync(user, role, CancellationToken))
                 {
                     return await UserAlreadyInRoleError(user, role);
                 }
diff --git a/test/Microsoft.AspNet.Identity.Test/UserManagerTest.cs b/test/Microsoft.AspNet.Identity.Test/UserManagerTest.cs
index 07bddee229..c63f1ac7a4 100644
--- a/test/Microsoft.AspNet.Identity.Test/UserManagerTest.cs
+++ b/test/Microsoft.AspNet.Identity.Test/UserManagerTest.cs
@@ -270,7 +270,7 @@ namespace Microsoft.AspNet.Identity.Test
             // Setup
             var store = new Mock<IUserRoleStore<TestUser>>();
             var user = new TestUser { UserName = "Foo" };
-            var roles = new string[] { "A", "B", "C" };
+            var roles = new string[] { "A", "B", "C", "C" };
             store.Setup(s => s.AddToRoleAsync(user, "A", CancellationToken.None))
                 .Returns(Task.FromResult(0))
                 .Verifiable();
@@ -280,8 +280,17 @@ namespace Microsoft.AspNet.Identity.Test
             store.Setup(s => s.AddToRoleAsync(user, "C", CancellationToken.None))
                 .Returns(Task.FromResult(0))
                 .Verifiable();
+
             store.Setup(s => s.UpdateAsync(user, CancellationToken.None)).ReturnsAsync(IdentityResult.Success).Verifiable();
-            store.Setup(s => s.GetRolesAsync(user, CancellationToken.None)).ReturnsAsync(new List<string>()).Verifiable();
+            store.Setup(s => s.IsInRoleAsync(user, "A", CancellationToken.None))
+                .Returns(Task.FromResult(false))
+                .Verifiable();
+            store.Setup(s => s.IsInRoleAsync(user, "B", CancellationToken.None))
+                .Returns(Task.FromResult(false))
+                .Verifiable();
+            store.Setup(s => s.IsInRoleAsync(user, "C", CancellationToken.None))
+                .Returns(Task.FromResult(false))
+                .Verifiable();
             var userManager = MockHelpers.TestUserManager<TestUser>(store.Object);
 
             // Act
@@ -290,6 +299,7 @@ namespace Microsoft.AspNet.Identity.Test
             // Assert
             Assert.True(result.Succeeded);
             store.VerifyAll();
+            store.Verify(s => s.AddToRoleAsync(user, "C", CancellationToken.None), Times.Once());
         }
 
         [Fact]
@@ -302,8 +312,10 @@ namespace Microsoft.AspNet.Identity.Test
             store.Setup(s => s.AddToRoleAsync(user, "A", CancellationToken.None))
                 .Returns(Task.FromResult(0))
                 .Verifiable();
-            store.Setup(s => s.GetRolesAsync(user, CancellationToken.None)).ReturnsAsync(new List<string> { "B" }).Verifiable();
-            var userManager = MockHelpers.TestUserManager<TestUser>(store.Object);
+            store.Setup(s => s.IsInRoleAsync(user, "B", CancellationToken.None))
+                .Returns(Task.FromResult(true))
+                .Verifiable();
+            var userManager = MockHelpers.TestUserManager(store.Object);
 
             // Act
             var result = await userManager.AddToRolesAsync(user, roles);
diff --git a/test/Shared/UserManagerTestBase.cs b/test/Shared/UserManagerTestBase.cs
index c864feec6d..fad54c739f 100644
--- a/test/Shared/UserManagerTestBase.cs
+++ b/test/Shared/UserManagerTestBase.cs
@@ -1405,6 +1405,23 @@ namespace Microsoft.AspNet.Identity.Test
             IdentityResultAssert.VerifyLogMessage(userMgr.Logger, $"User {await userMgr.GetUserIdAsync(user)} is already in role {roleName}.");
         }
 
+        [ConditionalTheory]
+        [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
+        public async Task AddUserToRolesIgnoresDuplicates()
+        {
+            var context = CreateTestContext();
+            var userMgr = CreateManager(context);
+            var roleMgr = CreateRoleManager(context);
+            var roleName = "addUserDupeTest" + Guid.NewGuid().ToString();
+            var role = CreateTestRole(roleName, useRoleNamePrefixAsRoleName: true);
+            var user = CreateTestUser();
+            IdentityResultAssert.IsSuccess(await userMgr.CreateAsync(user));
+            IdentityResultAssert.IsSuccess(await roleMgr.CreateAsync(role));
+            Assert.False(await userMgr.IsInRoleAsync(user, roleName));
+            IdentityResultAssert.IsSuccess(await userMgr.AddToRolesAsync(user, new[] { roleName, roleName }));
+            Assert.True(await userMgr.IsInRoleAsync(user, roleName));
+        }
+
         [ConditionalTheory]
         [FrameworkSkipCondition(RuntimeFrameworks.Mono)]
         public async Task CanFindRoleByNameWithManager()