diff --git a/Rx.NET/Source/tests/Tests.System.Reactive.Uwp.DeviceRunner/Tests.System.Reactive.Uwp.DeviceRunner.csproj b/Rx.NET/Source/tests/Tests.System.Reactive.Uwp.DeviceRunner/Tests.System.Reactive.Uwp.DeviceRunner.csproj
index 98fd72d650..610cc79141 100644
--- a/Rx.NET/Source/tests/Tests.System.Reactive.Uwp.DeviceRunner/Tests.System.Reactive.Uwp.DeviceRunner.csproj
+++ b/Rx.NET/Source/tests/Tests.System.Reactive.Uwp.DeviceRunner/Tests.System.Reactive.Uwp.DeviceRunner.csproj
@@ -156,6 +156,7 @@
   </PropertyGroup>
   <PropertyGroup>
     <SignAssembly>true</SignAssembly>
+    <DefineConstants Condition="$(SignAssembly) == 'true'">$(DefineConstants);SIGNED</DefineConstants>
     <UpdateAssemblyInfo>false</UpdateAssemblyInfo>
   </PropertyGroup>
   <PropertyGroup>
diff --git a/Rx.NET/Source/tests/Tests.System.Reactive/Tests/ImmutableListTest.cs b/Rx.NET/Source/tests/Tests.System.Reactive/Tests/ImmutableListTest.cs
index 81ac62fc35..3e3c4f3e33 100644
--- a/Rx.NET/Source/tests/Tests.System.Reactive/Tests/ImmutableListTest.cs
+++ b/Rx.NET/Source/tests/Tests.System.Reactive/Tests/ImmutableListTest.cs
@@ -4,7 +4,7 @@
 
 namespace ReactiveTests.Tests
 {
-#if !SIGNED
+#if SIGNED
     
     public class ImmutableListTest
     {