diff --git a/src/libraries/Common/tests/System/Net/Http/Http3LoopbackServer.cs b/src/libraries/Common/tests/System/Net/Http/Http3LoopbackServer.cs
index 1da9ee272eb9c..ff82861e6589e 100644
--- a/src/libraries/Common/tests/System/Net/Http/Http3LoopbackServer.cs
+++ b/src/libraries/Common/tests/System/Net/Http/Http3LoopbackServer.cs
@@ -24,7 +24,7 @@ public Http3LoopbackServer(QuicImplementationProvider quicImplementationProvider
         {
             options ??= new GenericLoopbackOptions();
 
-            _cert = Configuration.Certificates.GetSelfSigned13ServerCertificate();
+            _cert = Configuration.Certificates.GetServerCertificate();
 
             var sslOpts = new SslServerAuthenticationOptions
             {
@@ -35,7 +35,7 @@ public Http3LoopbackServer(QuicImplementationProvider quicImplementationProvider
                     new SslApplicationProtocol("h3-30"),
                     new SslApplicationProtocol("h3-29")
                 },
-                //ServerCertificate = _cert,
+                ServerCertificate = _cert,
                 ClientCertificateRequired = false
             };
 
diff --git a/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs b/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs
index 24392320c923c..0392966af0fbc 100644
--- a/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs
+++ b/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicConnection.cs
@@ -361,7 +361,10 @@ private ValueTask ShutdownAsync(
             QUIC_CONNECTION_SHUTDOWN_FLAGS Flags,
             long ErrorCode)
         {
-            Debug.Assert(!_state.ShutdownTcs.Task.IsCompleted);
+            if (_state.ShutdownTcs.Task.IsCompleted)
+            {
+                return ValueTask.CompletedTask;
+            }
 
             // Store the connection into the GCHandle'd state to prevent GC if user calls ShutdownAsync and gets rid of all references to the MsQuicConnection.
             Debug.Assert(_state.Connection == null);