diff --git a/PolyShim/NetCore21/BinaryPrimitives.cs b/PolyShim/NetCore21/BinaryPrimitives.cs
index c240c45..f3c5640 100644
--- a/PolyShim/NetCore21/BinaryPrimitives.cs
+++ b/PolyShim/NetCore21/BinaryPrimitives.cs
@@ -1,4 +1,4 @@
-#if (NETCOREAPP && !NETCOREAPP2_1_OR_GREATER) || (NETSTANDARD && !NETSTANDARD2_1_OR_GREATER) || NETFRAMEWORK
+#if !FEATURE_MEMORY
 #nullable enable
 #pragma warning disable CS0436