diff --git a/rust/src/fileio_asyncio.rs b/rust/src/fileio_asyncio.rs
index e9f063f21..2656e5afe 100644
--- a/rust/src/fileio_asyncio.rs
+++ b/rust/src/fileio_asyncio.rs
@@ -400,9 +400,8 @@ pub struct FIO_rust_compress_dst_projection_t {
     pub remove_destination: Option<FIO_rust_compress_dst_remove_fn>,
 }
 const _: () = {
-    let callback_offset = (3 * size_of::<usize>() + 5 * size_of::<c_int>() + size_of::<usize>()
-        - 1)
-        / size_of::<usize>()
+    let callback_offset = (3 * size_of::<usize>() + 5 * size_of::<c_int>())
+        .div_ceil(size_of::<usize>())
         * size_of::<usize>();
     assert!(std::mem::offset_of!(FIO_rust_compress_dst_projection_t, opaque) == 0);
     assert!(
@@ -467,7 +466,7 @@ const _: () = {
     );
     assert!(
         std::mem::offset_of!(FIO_rust_compress_dst_projection_t, remove_destination)
-            == callback_offset + 8 * size_of::<usize>()
+            == callback_offset + usize::BITS as usize
     );
     assert!(
         size_of::<FIO_rust_compress_dst_projection_t>() == callback_offset + 9 * size_of::<usize>()