diff --git a/appveyor.yml b/appveyor.yml
index d9e88cd..872f321 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,8 +1,6 @@
 version: '{build}'
 skip_tags: true
-image: Visual Studio 2017
-configuration: Release
-install:
+image: Visual Studio 2019
 build_script:
 - ps: ./Build.ps1
 test: off
diff --git a/src/Seq.Api/Client/SeqApiClient.cs b/src/Seq.Api/Client/SeqApiClient.cs
index f505450..13445df 100644
--- a/src/Seq.Api/Client/SeqApiClient.cs
+++ b/src/Seq.Api/Client/SeqApiClient.cs
@@ -14,6 +14,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.IO;
 using System.Net;
 using System.Net.Http;
@@ -56,7 +57,20 @@ public class SeqApiClient : IDisposable
         /// <param name="serverUrl">The base URL of the Seq server.</param>
         /// <param name="apiKey">An API key to use when making requests to the server, if required.</param>
         /// <param name="useDefaultCredentials">Whether default credentials will be sent with HTTP requests; the default is <c>true</c>.</param>
-        public SeqApiClient(string serverUrl, string apiKey = null, bool useDefaultCredentials = true)
+        [Obsolete("Prefer `SeqApiClient(serverUrl, apiKey, handler => handler.UseDefaultCredentials = true)` instead."), EditorBrowsable(EditorBrowsableState.Never)]
+        public SeqApiClient(string serverUrl, string apiKey, bool useDefaultCredentials)
+            : this(serverUrl, apiKey, handler => handler.UseDefaultCredentials = useDefaultCredentials)
+        {
+        }
+
+        /// <summary>
+        /// Construct a <see cref="SeqApiClient"/>.
+        /// </summary>
+        /// <param name="serverUrl">The base URL of the Seq server.</param>
+        /// <param name="apiKey">An API key to use when making requests to the server, if required.</param>
+        /// <param name="configureHttpClientHandler">An optional callback to configure the <see cref="HttpClientHandler"/> used when making HTTP requests
+        /// to the Seq API.</param>
+        public SeqApiClient(string serverUrl, string apiKey = null, Action<HttpClientHandler> configureHttpClientHandler = null)
         {
             ServerUrl = serverUrl ?? throw new ArgumentNullException(nameof(serverUrl));
 
@@ -65,10 +79,11 @@ public SeqApiClient(string serverUrl, string apiKey = null, bool useDefaultCrede
 
             var handler = new HttpClientHandler
             {
-                CookieContainer = _cookies,
-                UseDefaultCredentials = useDefaultCredentials
+                CookieContainer = _cookies
             };
 
+            configureHttpClientHandler?.Invoke(handler);
+
             var baseAddress = serverUrl;
             if (!baseAddress.EndsWith("/"))
                 baseAddress += "/";
diff --git a/src/Seq.Api/SeqConnection.cs b/src/Seq.Api/SeqConnection.cs
index 8388519..d7e7ba8 100644
--- a/src/Seq.Api/SeqConnection.cs
+++ b/src/Seq.Api/SeqConnection.cs
@@ -14,7 +14,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Net;
+using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
 using Seq.Api.Client;
@@ -27,7 +29,7 @@ namespace Seq.Api
     /// <summary>
     /// Exposes high-level (typed) interactions with the Seq API through various resource groups.
     /// </summary>
-    public class SeqConnection : ISeqConnection
+    public class SeqConnection : ISeqConnection, IDisposable
     {
         readonly object _sync = new object();
         readonly Dictionary<string, Task<ResourceGroup>> _resourceGroups = new Dictionary<string, Task<ResourceGroup>>();
@@ -39,12 +41,34 @@ public class SeqConnection : ISeqConnection
         /// <param name="serverUrl">The base URL of the Seq server.</param>
         /// <param name="apiKey">An API key to use when making requests to the server, if required.</param>
         /// <param name="useDefaultCredentials">Whether default credentials will be sent with HTTP requests; the default is <c>true</c>.</param>
-        public SeqConnection(string serverUrl, string apiKey = null, bool useDefaultCredentials = true)
+        [Obsolete("Prefer `SeqConnection(serverUrl, apiKey, handler => handler.UseDefaultCredentials = true)` instead."), EditorBrowsable(EditorBrowsableState.Never)]
+        public SeqConnection(string serverUrl, string apiKey, bool useDefaultCredentials)
         {
             if (serverUrl == null) throw new ArgumentNullException(nameof(serverUrl));
             Client = new SeqApiClient(serverUrl, apiKey, useDefaultCredentials);
         }
+
+        /// <summary>
+        /// Construct a <see cref="SeqConnection"/>.
+        /// </summary>
+        /// <param name="serverUrl">The base URL of the Seq server.</param>
+        /// <param name="apiKey">An API key to use when making requests to the server, if required.</param>
+        /// <param name="configureHttpClientHandler">An optional callback to configure the <see cref="HttpClientHandler"/> used when making HTTP requests
+        /// to the Seq API.</param>
+        public SeqConnection(string serverUrl, string apiKey = null, Action<HttpClientHandler> configureHttpClientHandler = null)
+        {
+            if (serverUrl == null) throw new ArgumentNullException(nameof(serverUrl));
+            Client = new SeqApiClient(serverUrl, apiKey, configureHttpClientHandler);
+        }
         
+        /// <summary>
+        /// <inheritdoc/>
+        /// </summary>
+        public void Dispose()
+        {
+            Client.Dispose();
+        }
+
         /// <summary>
         /// Access the lower-level <see cref="SeqApiClient"/> that can be used for resource-oriented navigation through
         /// the HTTP API.
diff --git a/test/Seq.Api.Tests/SeqConnectionTests.cs b/test/Seq.Api.Tests/SeqConnectionTests.cs
new file mode 100644
index 0000000..2c30f87
--- /dev/null
+++ b/test/Seq.Api.Tests/SeqConnectionTests.cs
@@ -0,0 +1,20 @@
+using Xunit;
+
+namespace Seq.Api.Tests
+{
+    public class SeqConnectionTests
+    {
+        [Fact]
+        public void WhenConstructedTheHandlerConfigurationCallbackIsCalled()
+        {
+            var callCount = 0;
+
+            using var _ = new SeqConnection("https://test.example.com", null, handler => { 
+                Assert.NotNull(handler);
+                ++callCount;
+            });
+
+            Assert.Equal(1, callCount);
+        }
+    }
+}