1 files changed, 4 insertions, 0 deletions
diff --git a/crypto/src/util/io/BaseInputStream.cs b/crypto/src/util/io/BaseInputStream.cs
index 8f5265fee..438583c75 100644
--- a/crypto/src/util/io/BaseInputStream.cs
+++ b/crypto/src/util/io/BaseInputStream.cs
@@ -1,7 +1,9 @@
 using System;
 using System.IO;
 using System.Threading;
+#if NETCOREAPP1_0_OR_GREATER || NET45_OR_GREATER || NETSTANDARD1_0_OR_GREATER
 using System.Threading.Tasks;
+#endif
 
 namespace Org.BouncyCastle.Utilities.IO
 {
@@ -19,10 +21,12 @@ namespace Org.BouncyCastle.Utilities.IO
         }
 #endif
 
+#if NETCOREAPP1_0_OR_GREATER || NET45_OR_GREATER || NETSTANDARD1_0_OR_GREATER
         public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
         {
             return Streams.CopyToAsync(this, destination, bufferSize, cancellationToken);
         }
+#endif
 
         public sealed override void Flush() {}
         public sealed override long Length { get { throw new NotSupportedException(); } }