diff --git a/ClosedXML_Tests/ClosedXML_Tests.csproj b/ClosedXML_Tests/ClosedXML_Tests.csproj
index e5137ce..a3e08fd 100644
--- a/ClosedXML_Tests/ClosedXML_Tests.csproj
+++ b/ClosedXML_Tests/ClosedXML_Tests.csproj
@@ -5,6 +5,10 @@
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <DefineConstants>$(AppVeyor)</DefineConstants>
+  </PropertyGroup>
+
   <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard1.6' ">
     <DefineConstants>$(DefineConstants);_NETSTANDARD_;_NETSTANDARD1_6_</DefineConstants>
   </PropertyGroup>