diff --git a/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs b/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs
index 3acfe7f189f4a..1a3b68c55c711 100644
--- a/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs
+++ b/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs
@@ -76,6 +76,9 @@ internal sealed class HttpConnectionPool : IDisposable
         private byte[]? _http2AltSvcOriginUri;
         internal readonly byte[]? _http2EncodedAuthorityHostHeader;
 
+        [SupportedOSPlatformGuard("linux")]
+        [SupportedOSPlatformGuard("macOS")]
+        [SupportedOSPlatformGuard("Windows")]
         private readonly bool _http3Enabled;
         private Http3Connection? _http3Connection;
         private SemaphoreSlim? _http3ConnectionCreateLock;
diff --git a/src/libraries/System.Net.Http/tests/TrimmingTests/HttpClientTest.cs b/src/libraries/System.Net.Http/tests/TrimmingTests/HttpClientTest.cs
index f6ec0a315f233..7ded3b5b65be8 100644
--- a/src/libraries/System.Net.Http/tests/TrimmingTests/HttpClientTest.cs
+++ b/src/libraries/System.Net.Http/tests/TrimmingTests/HttpClientTest.cs
@@ -9,6 +9,11 @@
 
 class Program
 {
+    [SupportedOSPlatformGuard("linux")]
+    [SupportedOSPlatformGuard("macOS")]
+    [SupportedOSPlatformGuard("Windows")]
+    private static bool IsHttp3Supported => (OperatingSystem.IsLinux() && !OperatingSystem.IsAndroid()) || OperatingSystem.IsWindows() || OperatingSystem.IsMacOS();
+
     static async Task<int> Main(string[] args)
     {
         using var client = new HttpClient();
@@ -19,12 +24,7 @@ static async Task<int> Main(string[] args)
         const string quicDll = "System.Net.Quic.dll";
         var quicDllExists = File.Exists(Path.Combine(AppContext.BaseDirectory, quicDll));
 
-        [SupportedOSPlatformGuard("linux")]
-        [SupportedOSPlatformGuard("macOS")]
-        [SupportedOSPlatformGuard("Windows")]
-        private readonly bool _http3Enabled = (OperatingSystem.IsLinux() && !OperatingSystem.IsAndroid()) || OperatingSystem.IsWindows() || OperatingSystem.IsMacOS();
-
-        if (_http3Enabled)
+        if (IsHttp3Supported)
         {
             Console.WriteLine($"Expected {quicDll} is {(quicDllExists ? "present - OK" : "missing - BAD")}.");
             return quicDllExists ? 100 : -1;