diff --git a/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj b/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj
index 5bc4008a1b..8ea0de0a32 100644
--- a/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj
+++ b/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions.csproj
@@ -10,6 +10,7 @@
     <NoWarn>CS1570;CS1571;CS1572;CS1573;CS1574;CS1591;$(NoWarn)</NoWarn>
     <EnableApiCheck>false</EnableApiCheck>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <DefineConstants>$(DefineConstants);KESTREL_BY_SOURCE</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>