diff --git a/ClosedXML/ClosedXML.csproj b/ClosedXML/ClosedXML.csproj
index 406116e..396ba4c 100644
--- a/ClosedXML/ClosedXML.csproj
+++ b/ClosedXML/ClosedXML.csproj
@@ -40,6 +40,7 @@
     <DocumentationFile>bin\Release\ClosedXML.xml</DocumentationFile>
     <NoWarn>1591</NoWarn>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup>
     <SignAssembly>true</SignAssembly>
diff --git a/ClosedXML_Examples/ClosedXML_Examples.csproj b/ClosedXML_Examples/ClosedXML_Examples.csproj
index 9f51673..2f42066 100644
--- a/ClosedXML_Examples/ClosedXML_Examples.csproj
+++ b/ClosedXML_Examples/ClosedXML_Examples.csproj
@@ -35,6 +35,7 @@
     <PlatformTarget>AnyCPU</PlatformTarget>
     <ErrorReport>prompt</ErrorReport>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup>
     <StartupObject>ClosedXML_Examples.Program</StartupObject>
diff --git a/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj b/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
index 7566bbf..7931620 100644
--- a/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
+++ b/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
@@ -34,6 +34,7 @@
     <PlatformTarget>AnyCPU</PlatformTarget>
     <ErrorReport>prompt</ErrorReport>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="DocumentFormat.OpenXml, Version=2.7.2.0, Culture=neutral, PublicKeyToken=8fb06cb64d019a17, processorArchitecture=MSIL">
diff --git a/ClosedXML_Tests/ClosedXML_Tests.csproj b/ClosedXML_Tests/ClosedXML_Tests.csproj
index a1c5279..72509bc 100644
--- a/ClosedXML_Tests/ClosedXML_Tests.csproj
+++ b/ClosedXML_Tests/ClosedXML_Tests.csproj
@@ -36,6 +36,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <Prefer32Bit>false</Prefer32Bit>
+    <LangVersion>6</LangVersion>
   </PropertyGroup>
   <PropertyGroup>
     <SignAssembly>true</SignAssembly>