add 'TargetFramework' .NET Core
diff --git a/src/Log4netAssemblyInfo.cs b/src/Log4netAssemblyInfo.cs
index 60337cc..c6a3b7b 100644
--- a/src/Log4netAssemblyInfo.cs
+++ b/src/Log4netAssemblyInfo.cs
@@ -59,6 +59,8 @@
         public const string TargetFramework = "Mono";
 #elif SSCLI
         public const string TargetFramework = "Shared Source CLI";
+#elif NETSTANDARD1_3
+        public const string TargetFramework = ".NET Core";
 #else
         public const string TargetFramework = "Unknown";
 #endif