diff --git a/FortnoxAPILibrary.Tests/BaseConnectorTests.cs b/FortnoxAPILibrary.Tests/BaseConnectorTests.cs
index 8d0ce16a..eb3f9de5 100644
--- a/FortnoxAPILibrary.Tests/BaseConnectorTests.cs
+++ b/FortnoxAPILibrary.Tests/BaseConnectorTests.cs
@@ -23,7 +23,8 @@ public void Test_Find_ParamsAdded()
         {
             var connector = new CustomerConnector
             {
-                Search = new CustomerSearch(){
+                Search = new CustomerSearch()
+                {
                     Name = "TestName",
                     City = "TestCity",
                     LastModified = new DateTime(2000, 01, 01, 20, 10, 05), //2000-01-20 20:10:05
@@ -198,5 +199,17 @@ private static int GetNeededPages(int totalSize, int pageSize)
         {
             return (int) Math.Ceiling(totalSize / (float) pageSize);
         }
+
+        [Ignore("Requires new authorization code.")]
+        [TestMethod]
+        public void TestAuth()
+        {
+            var authorizationCode = "Placeholder";
+            var authConnector = new AuthorizationConnector();
+            var token = authConnector.GetAccessToken(authorizationCode, TestCredentials.Client_Secret);
+
+            MyAssert.HasNoError(authConnector);
+            Assert.IsNotNull(token);
+        }
     }
 }
diff --git a/FortnoxAPILibrary.Tests/MyAssert.cs b/FortnoxAPILibrary.Tests/MyAssert.cs
index f7ce355c..00bb9f9a 100644
--- a/FortnoxAPILibrary.Tests/MyAssert.cs
+++ b/FortnoxAPILibrary.Tests/MyAssert.cs
@@ -9,7 +9,7 @@ public static class MyAssert
         /// Checks if the last request was successfull
         /// </summary>
         /// <param name="connector"></param>
-        public static void HasNoError(IConnector connector)
+        public static void HasNoError(IBaseConnector connector)
         {
             if (connector.HasError)
                 throw new AssertFailedException($"Request failed due to '{connector.Error.Message}'.");
diff --git a/FortnoxAPILibrary/BaseClient.cs b/FortnoxAPILibrary/BaseClient.cs
index 50f696d6..e2004ee4 100644
--- a/FortnoxAPILibrary/BaseClient.cs
+++ b/FortnoxAPILibrary/BaseClient.cs
@@ -48,10 +48,13 @@ public BaseClient()
             UseRateLimiter = ConnectionSettings.UseRateLimiter;
         }
 
-        public async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request)
+        public async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool addAuthHeaders = true)
         {
-            request.Headers.Add(AccessTokenHeader, AccessToken);
-            request.Headers.Add(ClientSecretHeader, ClientSecret);
+            if (addAuthHeaders)
+            {
+                request.Headers.Add(AccessTokenHeader, AccessToken);
+                request.Headers.Add(ClientSecretHeader, ClientSecret);
+            }
 
             if (UseRateLimiter)
                 await Throttle();
diff --git a/FortnoxAPILibrary/Connectors/AuthorizationConnector.cs b/FortnoxAPILibrary/Connectors/AuthorizationConnector.cs
index 27e352e4..04a8e888 100644
--- a/FortnoxAPILibrary/Connectors/AuthorizationConnector.cs
+++ b/FortnoxAPILibrary/Connectors/AuthorizationConnector.cs
@@ -27,19 +27,19 @@ public string GetAccessToken(string authorizationCode, string clientSecret)
         public async Task<string> GetAccessTokenAsync(string authorizationCode, string clientSecret)
         {
             if (string.IsNullOrEmpty(authorizationCode))
-                return string.Empty;
+                return null;
             if (string.IsNullOrEmpty(clientSecret))
-                return string.Empty;
+                return null;
 
             try
             {
                 var wr = SetupRequest(BaseUrl, authorizationCode, clientSecret);
-                using var response = await HttpClient.SendAsync(wr).ConfigureAwait(false);
+                using var response = await HttpClient.SendAsync(wr, false).ConfigureAwait(false);
 
                 if (!response.IsSuccessStatusCode)
                 {
                     Error = ErrorHandler.HandleError(response);
-                    return string.Empty;
+                    return null;
                 }
 
                 var json = response.Content.ReadAsStringAsync().Result;
@@ -51,7 +51,7 @@ public async Task<string> GetAccessTokenAsync(string authorizationCode, string c
             catch (HttpRequestException we)
             {
                 Error = ErrorHandler.HandleConnectionException(we);
-                return string.Empty;
+                return null;
             }
         }
 
@@ -60,8 +60,8 @@ private HttpRequestMessage SetupRequest(string requestUriString, string authoriz
             Error = null;
 
             var wr = new HttpRequestMessage(HttpMethod.Get,  requestUriString);
-            wr.Headers.Add("authorization-code", authorizationCode);
-            wr.Headers.Add("client-secret", clientSecret);
+            wr.Headers.Add("Authorization-Code", authorizationCode);
+            wr.Headers.Add("Client-Secret", clientSecret);
             wr.Headers.Add("Accept", "application/json");
             return wr;
         }
diff --git a/FortnoxAPILibrary/FortnoxAPILibrary.csproj b/FortnoxAPILibrary/FortnoxAPILibrary.csproj
index 9803d1e9..a60c6f48 100644
--- a/FortnoxAPILibrary/FortnoxAPILibrary.csproj
+++ b/FortnoxAPILibrary/FortnoxAPILibrary.csproj
@@ -4,7 +4,7 @@
     <TargetFramework>netstandard2.0</TargetFramework>
 	<LangVersion>8</LangVersion>
 	<PackageId>Fortnox.NET.SDK</PackageId>
-	<Version>3.5.0</Version>
+	<Version>3.5.1</Version>
 	<Authors>Richard Randak</Authors>
 	<Company>Softwerk AB</Company>
 	<Description>Official .NET SDK for Fortnox API. This package is on behalf of Fortnox AB developed and maintained by Softwerk AB. For more information please visit our repository on Github.</Description>