diff --git a/src/Microsoft.Owin.Security.ActiveDirectory/WsFedCachingSecurityTokenProvider.cs b/src/Microsoft.Owin.Security.ActiveDirectory/WsFedCachingSecurityTokenProvider.cs
index f7b00316..6039c9df 100644
--- a/src/Microsoft.Owin.Security.ActiveDirectory/WsFedCachingSecurityTokenProvider.cs
+++ b/src/Microsoft.Owin.Security.ActiveDirectory/WsFedCachingSecurityTokenProvider.cs
@@ -19,8 +19,6 @@ namespace Microsoft.Owin.Security.ActiveDirectory
     {
         private readonly TimeSpan _refreshInterval = new TimeSpan(1, 0, 0, 0);
 
-        private readonly ReaderWriterLockSlim _synclock = new ReaderWriterLockSlim();
-
         private readonly string _metadataEndpoint;
 
         private readonly TimeSpan _backchannelTimeout;
@@ -63,16 +61,8 @@ namespace Microsoft.Owin.Security.ActiveDirectory
         {
             get
             {
-                RetrieveMetadata();
-                _synclock.EnterReadLock();
-                try
-                {
-                    return _issuer;
-                }
-                finally
-                {
-                    _synclock.ExitReadLock();
-                }
+                RefreshMetadata();
+                return _issuer;
             }
         }
 
@@ -86,39 +76,40 @@ namespace Microsoft.Owin.Security.ActiveDirectory
         {
             get
             {
-                RetrieveMetadata();
-                _synclock.EnterReadLock();
-                try
-                {
-                    return _tokens;
-                }
-                finally
-                {
-                    _synclock.ExitReadLock();
-                }
+                RefreshMetadata();
+                return _tokens;
             }
         }
 
-        private void RetrieveMetadata()
+        private void RefreshMetadata()
         {
             if (_syncAfter >= DateTimeOffset.UtcNow)
             {
                 return;
             }
 
-            _synclock.EnterWriteLock();
-            try
+            // Queue a refresh, but discourage other threads from doing so.
+            _syncAfter = DateTimeOffset.UtcNow + _refreshInterval;
+            ThreadPool.UnsafeQueueUserWorkItem(state =>
             {
-                IssuerSigningKeys metaData = WsFedMetadataRetriever.GetSigningKeys(_metadataEndpoint,
-                    _backchannelTimeout, _backchannelHttpHandler);
-                _issuer = metaData.Issuer;
-                _tokens = metaData.Tokens;
-                _syncAfter = DateTimeOffset.UtcNow + _refreshInterval;
-            }
-            finally
-            {
-                _synclock.ExitWriteLock();
-            }
+                try
+                {
+                    RetrieveMetadata();
+                }
+                catch (Exception)
+                {
+                    // Don't throw exceptions on background threads.
+                }
+            }, state: null);
+        }
+
+        private void RetrieveMetadata()
+        {
+            _syncAfter = DateTimeOffset.UtcNow + _refreshInterval;
+            IssuerSigningKeys metaData = WsFedMetadataRetriever.GetSigningKeys(_metadataEndpoint,
+                _backchannelTimeout, _backchannelHttpHandler);
+            _issuer = metaData.Issuer;
+            _tokens = metaData.Tokens;
         }
     }
 }
diff --git a/src/Microsoft.Owin.Security.Google/GoogleOAuth2AuthenticationHandler.cs b/src/Microsoft.Owin.Security.Google/GoogleOAuth2AuthenticationHandler.cs
index b0e24392..2b1e85aa 100644
--- a/src/Microsoft.Owin.Security.Google/GoogleOAuth2AuthenticationHandler.cs
+++ b/src/Microsoft.Owin.Security.Google/GoogleOAuth2AuthenticationHandler.cs
@@ -195,7 +195,9 @@ namespace Microsoft.Owin.Security.Google
 
                 AddQueryString(queryStrings, properties, "access_type", Options.AccessType);
                 AddQueryString(queryStrings, properties, "approval_prompt");
+                AddQueryString(queryStrings, properties, "prompt");
                 AddQueryString(queryStrings, properties, "login_hint");
+                AddQueryString(queryStrings, properties, "include_granted_scopes");
 
                 string state = Options.StateDataFormat.Protect(properties);
                 queryStrings.Add("state", state);
diff --git a/tests/Katana.Sandbox.WebServer/Startup.cs b/tests/Katana.Sandbox.WebServer/Startup.cs
index 90c6ad59..bfbd67f2 100644
--- a/tests/Katana.Sandbox.WebServer/Startup.cs
+++ b/tests/Katana.Sandbox.WebServer/Startup.cs
@@ -214,7 +214,10 @@ namespace Katana.Sandbox.WebServer
             {
                 map.Run(context =>
                 {
-                    context.Authentication.Challenge(new AuthenticationProperties() { RedirectUri = "/" }, context.Request.Query["scheme"]);
+                    var properties = new AuthenticationProperties();
+                    properties.RedirectUri = "/"; // Go back to the home page after authenticating.
+                    properties.Dictionary["prompt"] = "select_account"; // Google
+                    context.Authentication.Challenge(properties, context.Request.Query["scheme"]);
                     return Task.FromResult(0);
                 });
             });
diff --git a/tests/Microsoft.Owin.Security.Tests/Google/GoogleOAuth2MiddlewareTests.cs b/tests/Microsoft.Owin.Security.Tests/Google/GoogleOAuth2MiddlewareTests.cs
index e546266d..b3838a3d 100644
--- a/tests/Microsoft.Owin.Security.Tests/Google/GoogleOAuth2MiddlewareTests.cs
+++ b/tests/Microsoft.Owin.Security.Tests/Google/GoogleOAuth2MiddlewareTests.cs
@@ -47,7 +47,9 @@ namespace Microsoft.Owin.Security.Tests.Google
 
             location.ShouldNotContain("access_type=");
             location.ShouldNotContain("approval_prompt=");
+            location.ShouldNotContain("prompt=");
             location.ShouldNotContain("login_hint=");
+            location.ShouldNotContain("include_granted_scopes=");
         }
 
         [Fact]
@@ -162,7 +164,9 @@ namespace Microsoft.Owin.Security.Tests.Google
                                 { "scope", "https://www.googleapis.com/auth/plus.login" },
                                 { "access_type", "offline" },
                                 { "approval_prompt", "force" },
-                                { "login_hint", "test@example.com" }
+                                { "prompt", "consent" },
+                                { "login_hint", "test@example.com" },
+                                { "include_granted_scopes", "true" }
                             }), "Google");
                         res.StatusCode = 401;
                     }
@@ -175,7 +179,9 @@ namespace Microsoft.Owin.Security.Tests.Google
             query.ShouldContain("scope=" + Uri.EscapeDataString("https://www.googleapis.com/auth/plus.login"));
             query.ShouldContain("access_type=offline");
             query.ShouldContain("approval_prompt=force");
+            query.ShouldContain("prompt=consent");
             query.ShouldContain("login_hint=" + Uri.EscapeDataString("test@example.com"));
+            query.ShouldContain("include_granted_scopes=true");
         }
 
         [Fact]