diff --git a/rust/src/fileio_asyncio.rs b/rust/src/fileio_asyncio.rs
index cd4a7477f..a9e7d2ff2 100644
--- a/rust/src/fileio_asyncio.rs
+++ b/rust/src/fileio_asyncio.rs
@@ -1104,9 +1104,8 @@ pub struct FIO_rust_zstd_compress_projection_t {
     pub adaptive_diagnostic: Option<FIO_rust_zstd_adaptive_diagnostic_fn>,
 }
 const _: () = {
-    let callback_offset = (14 * size_of::<usize>() + 5 * size_of::<c_int>() + size_of::<usize>()
-        - 1)
-        / size_of::<usize>()
+    let callback_offset = (14 * size_of::<usize>() + 5 * size_of::<c_int>())
+        .div_ceil(size_of::<usize>())
         * size_of::<usize>();
     assert!(
         std::mem::offset_of!(FIO_rust_zstd_compress_projection_t, adaptive_mode)