diff --git a/src/Serilog/Serilog.csproj b/src/Serilog/Serilog.csproj
index 0e6af3504..8643248d6 100644
--- a/src/Serilog/Serilog.csproj
+++ b/src/Serilog/Serilog.csproj
@@ -66,7 +66,7 @@
   </PropertyGroup>
 
   <PropertyGroup Condition=" '$(TargetFramework)' == 'net46' ">
-    <DefineConstants>$(DefineConstants);ASYNCLOCAL</DefineConstants>
+    <DefineConstants>$(DefineConstants);ASYNCLOCAL;HASHTABLE</DefineConstants>
   </PropertyGroup>
 
   <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard1.3' ">