diff --git a/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs b/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs
index 361ed351e84084..c0ef253f9d12c0 100644
--- a/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs
+++ b/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs
@@ -103,7 +103,7 @@ internal HttpListenerRequest() { }
         public System.Net.TransportContext TransportContext { get { throw null; } }
         public System.Uri? Url { get { throw null; } }
         public System.Uri? UrlReferrer { get { throw null; } }
-        public string UserAgent { get { throw null; } }
+        public string? UserAgent { get { throw null; } }
         public string UserHostAddress { get { throw null; } }
         public string UserHostName { get { throw null; } }
         public string[]? UserLanguages { get { throw null; } }
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
index 473ae22c415b0c..5cd8253625065b 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
@@ -202,7 +202,7 @@ public NameValueCollection QueryString
 
         private string RequestScheme => IsSecureConnection ? UriScheme.Https : UriScheme.Http;
 
-        public string UserAgent => Headers[HttpKnownHeaderNames.UserAgent]!;
+        public string? UserAgent => Headers[HttpKnownHeaderNames.UserAgent];
 
         public string UserHostAddress => LocalEndPoint!.ToString();