diff --git a/src/Shared/IPaymoApiClient.cs b/src/Shared/IPaymoApiClient.cs
new file mode 100644
index 0000000..c35a3d5
--- /dev/null
+++ b/src/Shared/IPaymoApiClient.cs
@@ -0,0 +1,6 @@
+namespace Novaloop.PaymoApi.Shared
+{
+    public interface IPaymoApiClient
+    {
+    }
+}
\ No newline at end of file
diff --git a/src/Shared/PaymoApiClient.cs b/src/Shared/PaymoApiClient.cs
index c347a9e..6ad3f46 100644
--- a/src/Shared/PaymoApiClient.cs
+++ b/src/Shared/PaymoApiClient.cs
@@ -2,7 +2,7 @@ using System.Net.Http;
 
 namespace Novaloop.PaymoApi.Shared
 {
-    public class PaymoApiClient
+    public class PaymoApiClient : IPaymoApiClient
     {
         public PaymoApiClient(HttpClient client)
         {
diff --git a/tests/Novaloop.PaymoApi.Tests.csproj b/tests/Novaloop.PaymoApi.Tests.csproj
index c0dc1ac..19866ac 100644
--- a/tests/Novaloop.PaymoApi.Tests.csproj
+++ b/tests/Novaloop.PaymoApi.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>netstandard2.0</TargetFramework>
 
     <IsPackable>false</IsPackable>
   </PropertyGroup>