diff --git a/rust/kernel/sync/atomic/predefine.rs b/rust/kernel/sync/atomic/predefine.rs
index 45a17985cda4..0fca1ba3c2db 100644
--- a/rust/kernel/sync/atomic/predefine.rs
+++ b/rust/kernel/sync/atomic/predefine.rs
@@ -35,12 +35,23 @@ fn rhs_into_delta(rhs: i64) -> i64 {
 // as `isize` and `usize`, and `isize` and `usize` are always bi-directional transmutable to
 // `isize_atomic_repr`, which also always implements `AtomicImpl`.
 #[allow(non_camel_case_types)]
+#[cfg(not(testlib))]
 #[cfg(not(CONFIG_64BIT))]
 type isize_atomic_repr = i32;
 #[allow(non_camel_case_types)]
+#[cfg(not(testlib))]
 #[cfg(CONFIG_64BIT)]
 type isize_atomic_repr = i64;
 
+#[allow(non_camel_case_types)]
+#[cfg(testlib)]
+#[cfg(target_pointer_width = "32")]
+type isize_atomic_repr = i32;
+#[allow(non_camel_case_types)]
+#[cfg(testlib)]
+#[cfg(target_pointer_width = "64")]
+type isize_atomic_repr = i64;
+
 // Ensure size and alignment requirements are checked.
 static_assert!(size_of::<isize>() == size_of::<isize_atomic_repr>());
 static_assert!(align_of::<isize>() == align_of::<isize_atomic_repr>());