diff --git a/src/libraries/System.Net.Http/ref/System.Net.Http.cs b/src/libraries/System.Net.Http/ref/System.Net.Http.cs
index 1652b5804ae81..46d2b57abfc78 100644
--- a/src/libraries/System.Net.Http/ref/System.Net.Http.cs
+++ b/src/libraries/System.Net.Http/ref/System.Net.Http.cs
@@ -277,8 +277,10 @@ public HttpRequestOptionsKey(string key) {}
         public string Key { get { throw null; } }
     }
 
-    public sealed class HttpRequestOptions : System.Collections.Generic.IDictionary<string, object?>
+    public sealed class HttpRequestOptions : System.Collections.Generic.IDictionary<string, object?>, System.Collections.Generic.IReadOnlyDictionary<string, object?>
     {
+        bool System.Collections.Generic.IReadOnlyDictionary<string, object?>.ContainsKey(string key) { throw null; }
+        int System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<string, object?>>.Count { get { throw null; } }
         void System.Collections.Generic.IDictionary<string, object?>.Add(string key, object? value) { throw null; }
         System.Collections.Generic.ICollection<string> System.Collections.Generic.IDictionary<string, object?>.Keys { get { throw null; } }
         System.Collections.Generic.ICollection<object?> System.Collections.Generic.IDictionary<string, object?>.Values { get { throw null; } }
@@ -297,6 +299,10 @@ public sealed class HttpRequestOptions : System.Collections.Generic.IDictionary<
         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw null; }
         public bool TryGetValue<TValue>(HttpRequestOptionsKey<TValue> key, [MaybeNullWhen(false)] out TValue value) { throw null; }
         public void Set<TValue>(HttpRequestOptionsKey<TValue> key, TValue value) { throw null; }
+        bool System.Collections.Generic.IReadOnlyDictionary<string, object?>.TryGetValue(string key, out object? value) { throw null; }
+        object? System.Collections.Generic.IReadOnlyDictionary<string, object?>.this[string key] { get { throw null; } }
+        System.Collections.Generic.IEnumerable<string> System.Collections.Generic.IReadOnlyDictionary<string, object?>.Keys { get { throw null; } }
+        System.Collections.Generic.IEnumerable<object?> System.Collections.Generic.IReadOnlyDictionary<string, object?>.Values { get { throw null; } }
     }
 
     public partial class HttpResponseMessage : System.IDisposable
diff --git a/src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestOptions.cs b/src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestOptions.cs
index 20116559c8930..75cb6d8d7e6e1 100644
--- a/src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestOptions.cs
+++ b/src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestOptions.cs
@@ -9,9 +9,13 @@ namespace System.Net.Http
     /// <summary>
     /// Represents a collection of options for an HTTP request.
     /// </summary>
-    public sealed class HttpRequestOptions : IDictionary<string, object?>
+    public sealed class HttpRequestOptions : IDictionary<string, object?>, IReadOnlyDictionary<string, object?>
     {
         private Dictionary<string, object?> Options { get; } = new Dictionary<string, object?>();
+        bool IReadOnlyDictionary<string, object?>.TryGetValue(string key, out object? value) => Options.TryGetValue(key, out value);
+        object? IReadOnlyDictionary<string, object?>.this[string key] => Options[key];
+        IEnumerable<string> IReadOnlyDictionary<string, object?>.Keys => Options.Keys;
+        IEnumerable<object?> IReadOnlyDictionary<string, object?>.Values => Options.Values;
         object? IDictionary<string, object?>.this[string key]
         {
             get
@@ -38,7 +42,9 @@ public sealed class HttpRequestOptions : IDictionary<string, object?>
         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => ((System.Collections.IEnumerable)Options).GetEnumerator();
         bool IDictionary<string, object?>.Remove(string key) => Options.Remove(key);
         bool ICollection<KeyValuePair<string, object?>>.Remove(KeyValuePair<string, object?> item) => ((IDictionary<string, object?>)Options).Remove(item);
+        bool IReadOnlyDictionary<string, object?>.ContainsKey(string key) => Options.ContainsKey(key);
         bool IDictionary<string, object?>.TryGetValue(string key, out object? value) => Options.TryGetValue(key, out value);
+        int IReadOnlyCollection<KeyValuePair<string, object?>>.Count => Options.Count;
 
         /// <summary>
         /// Initializes a new instance of the HttpRequestOptions class.