diff --git a/src/Microsoft.AspNet.Identity/PrincipalExtensions.cs b/src/Microsoft.AspNet.Identity/PrincipalExtensions.cs
index c01cb0778c..669af4cfa3 100644
--- a/src/Microsoft.AspNet.Identity/PrincipalExtensions.cs
+++ b/src/Microsoft.AspNet.Identity/PrincipalExtensions.cs
@@ -18,13 +18,14 @@ namespace System.Security.Principal
         /// <param name="principal">The <see cref="IPrincipal"/> instance this method extends.</param>
         /// <returns>The Name claim value, or null if the claim is not present.</returns>
         /// <remarks>The name claim is identified by <see cref="ClaimsIdentity.DefaultNameClaimType"/>.</remarks>
-        public static string GetUserName(this ClaimsPrincipal principal)
+        public static string GetUserName(this IPrincipal principal)
         {
             if (principal == null)
             {
                 throw new ArgumentNullException(nameof(principal));
             }
-            return principal.FindFirstValue(ClaimsIdentity.DefaultNameClaimType);
+            var cp = principal as ClaimsPrincipal;
+            return cp != null ? cp.FindFirstValue(ClaimsIdentity.DefaultNameClaimType) : null;
         }
 
         /// <summary>
@@ -33,13 +34,14 @@ namespace System.Security.Principal
         /// <param name="principal">The <see cref="IPrincipal"/> instance this method extends.</param>
         /// <returns>The User ID claim value, or null if the claim is not present.</returns>
         /// <remarks>The name claim is identified by <see cref="ClaimTypes.NameIdentifier"/>.</remarks>
-        public static string GetUserId(this ClaimsPrincipal principal)
+        public static string GetUserId(this IPrincipal principal)
         {
             if (principal == null)
             {
                 throw new ArgumentNullException(nameof(principal));
             }
-            return principal.FindFirstValue(ClaimTypes.NameIdentifier);
+            var ci = principal as ClaimsPrincipal;
+            return ci != null ? ci.FindFirstValue(ClaimTypes.NameIdentifier) : null;
         }
 
         /// <summary>
@@ -47,14 +49,15 @@ namespace System.Security.Principal
         /// </summary>
         /// <param name="principal">The <see cref="IPrincipal"/> instance this method extends.</param>
         /// <returns>True if the user is logged in with identity.</returns>
-        public static bool IsSignedIn(this ClaimsPrincipal principal)
+        public static bool IsSignedIn(this IPrincipal principal)
         {
             if (principal == null)
             {
                 throw new ArgumentNullException(nameof(principal));
             }
-            return principal.Identities != null && 
-                principal.Identities.Any(i => i.AuthenticationType == IdentityOptions.ApplicationCookieAuthenticationType);
+            var p = principal as ClaimsPrincipal;
+            return p?.Identities != null && 
+                p.Identities.Any(i => i.AuthenticationType == IdentityOptions.ApplicationCookieAuthenticationType);
         }
 
         /// <summary>
diff --git a/test/Microsoft.AspNet.Identity.Test/PrincipalExtensionsTest.cs b/test/Microsoft.AspNet.Identity.Test/PrincipalExtensionsTest.cs
index 6d63e70e49..8a2e5b3a47 100644
--- a/test/Microsoft.AspNet.Identity.Test/PrincipalExtensionsTest.cs
+++ b/test/Microsoft.AspNet.Identity.Test/PrincipalExtensionsTest.cs
@@ -15,12 +15,21 @@ namespace Microsoft.AspNet.Identity.Test
         [Fact]
         public void IdentityNullCheckTest()
         {
+            IPrincipal p = null;
+            Assert.Throws<ArgumentNullException>("principal", () => p.GetUserId());
+            Assert.Throws<ArgumentNullException>("principal", () => p.GetUserName());
             ClaimsPrincipal cp = null;
-            Assert.Throws<ArgumentNullException>("principal", () => cp.GetUserId());
-            Assert.Throws<ArgumentNullException>("principal", () => cp.GetUserName());
             Assert.Throws<ArgumentNullException>("principal", () => cp.FindFirstValue(null));
         }
 
+        [Fact]
+        public void IdentityNullIfNotClaimsIdentityTest()
+        {
+            IPrincipal identity = new TestPrincipal();
+            Assert.Null(identity.GetUserId());
+            Assert.Null(identity.GetUserName());
+        }
+
         [Fact]
         public void UserNameAndIdTest()
         {
@@ -73,5 +82,39 @@ namespace Microsoft.AspNet.Identity.Test
                 },
                 ExternalAuthenticationScheme));
         }
+
+        private class TestPrincipal : IPrincipal
+        {
+            public IIdentity Identity
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public bool IsInRole(string role)
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        private class TestIdentity : IIdentity
+        {
+            public string AuthenticationType
+            {
+                get { throw new NotImplementedException(); }
+            }
+
+            public bool IsAuthenticated
+            {
+                get { throw new NotImplementedException(); }
+            }
+
+            public string Name
+            {
+                get { throw new NotImplementedException(); }
+            }
+        }
     }
 }
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