diff --git a/src/RestSharp/RestClient.cs b/src/RestSharp/RestClient.cs
index f4fe00932..00f8b9353 100644
--- a/src/RestSharp/RestClient.cs
+++ b/src/RestSharp/RestClient.cs
@@ -210,7 +210,7 @@ public RestClient(
     static void ConfigureHttpClient(HttpClient httpClient, RestClientOptions options) {
         if (options.MaxTimeout > 0) httpClient.Timeout = TimeSpan.FromMilliseconds(options.MaxTimeout);
 
-        if (options.UserAgent != null && httpClient.DefaultRequestHeaders.UserAgent.All(x => x.Product?.Name != options.UserAgent)) {
+        if (options.UserAgent != null && httpClient.DefaultRequestHeaders.UserAgent.All(x => $"{x.Product?.Name}/{x.Product?.Version}" != options.UserAgent)) {
             httpClient.DefaultRequestHeaders.TryAddWithoutValidation(KnownHeaders.UserAgent, options.UserAgent);
         }
 
diff --git a/test/RestSharp.Tests/RestClientTests.cs b/test/RestSharp.Tests/RestClientTests.cs
index 7dd4fe618..c99e2fc88 100644
--- a/test/RestSharp.Tests/RestClientTests.cs
+++ b/test/RestSharp.Tests/RestClientTests.cs
@@ -116,4 +116,19 @@ public void Should_use_new_httpClient_instance() {
 
         client1.HttpClient.Should().NotBeSameAs(client2.HttpClient);
     }
+
+    [Fact]
+    public void ConfigureHttpClient_does_not_duplicate_user_agent_for_same_client() {
+        // arrange
+        var httpClient = new HttpClient();
+        var clientOptions = new RestClientOptions();
+
+        // act
+        var restClient1 = new RestClient(httpClient, clientOptions);
+        var restClient2 = new RestClient(httpClient, clientOptions);
+
+        // assert
+        Assert.Contains(httpClient.DefaultRequestHeaders.UserAgent, agent => $"{agent.Product.Name}/{agent.Product.Version}" == clientOptions.UserAgent);
+        Assert.Single(httpClient.DefaultRequestHeaders.UserAgent);
+    }
 }