diff --git a/ClosedXML/ClosedXML.csproj b/ClosedXML/ClosedXML.csproj
index 8b7e9cc..f2c4e16 100644
--- a/ClosedXML/ClosedXML.csproj
+++ b/ClosedXML/ClosedXML.csproj
@@ -42,6 +42,7 @@
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
     <PackageReference Include="DocumentFormat.OpenXml" Version="2.7.2" />
+    <Reference Include="Microsoft.CSharp" />
     <Reference Include="WindowsBase" />
   </ItemGroup>
 
diff --git a/ClosedXML_Tests/ClosedXML_Tests.csproj b/ClosedXML_Tests/ClosedXML_Tests.csproj
index b830716..3dce604 100644
--- a/ClosedXML_Tests/ClosedXML_Tests.csproj
+++ b/ClosedXML_Tests/ClosedXML_Tests.csproj
@@ -49,6 +49,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
+    <Reference Include="Microsoft.CSharp" />
     <Reference Include="WindowsBase" />
   </ItemGroup>