diff --git a/tests/Microsoft.DotNet.Docker.Tests/TestSolution.cs b/tests/Microsoft.DotNet.Docker.Tests/TestSolution.cs
index b50cc4c669..0125aa300a 100644
--- a/tests/Microsoft.DotNet.Docker.Tests/TestSolution.cs
+++ b/tests/Microsoft.DotNet.Docker.Tests/TestSolution.cs
@@ -59,7 +59,7 @@ private string CreateTestSolutionWithSdkImage(string solutionDir, string appType
             string nuGetConfigFileName = "NuGet.config";
             if (Config.IsInternal)
             {
-                nuGetConfigFileName += "NuGet.config.internal";
+                nuGetConfigFileName = "NuGet.config.internal";
             }
             else if (Config.IsNightlyRepo)
             {