diff --git a/Rx/NET/Source/Microsoft.Reactive.Testing/ReactiveAssert.cs b/Rx/NET/Source/Microsoft.Reactive.Testing/ReactiveAssert.cs
index e9715a4..86cd62e 100644
--- a/Rx/NET/Source/Microsoft.Reactive.Testing/ReactiveAssert.cs
+++ b/Rx/NET/Source/Microsoft.Reactive.Testing/ReactiveAssert.cs
@@ -8,7 +8,9 @@
 using System.Reactive.Disposables;
 using System.Reactive.Linq;
 
-#if WINDOWS8
+#if NUNIT
+using NUnit.Framework;
+#elif WINDOWS8
 using Microsoft.VisualStudio.TestPlatform.UnitTestFramework;
 #else
 using Microsoft.VisualStudio.TestTools.UnitTesting;