diff --git a/rust/src/fileio_asyncio.rs b/rust/src/fileio_asyncio.rs
index 2f1faac2a..fc4e0ee31 100644
--- a/rust/src/fileio_asyncio.rs
+++ b/rust/src/fileio_asyncio.rs
@@ -361,7 +361,7 @@ const _: () = {
     );
     assert!(
         size_of::<FIO_rust_compress_src_projection_t>()
-            == 3 * size_of::<usize>() + 4 * size_of::<c_int>() + 8 * size_of::<usize>()
+            == 3 * size_of::<usize>() + 4 * size_of::<c_int>() + usize::BITS as usize
     );
 };