diff --git a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs
index f59fed9e..1518830a 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs
@@ -27,7 +27,7 @@ internal sealed partial class Unpack : BitInput, IRarUnpack
         if (!disposed)
         {
             base.Dispose();
-            if (!externalWindow)
+            if (!externalWindow && window is not null)
             {
                 ArrayPool<byte>.Shared.Return(window);
                 window = null;