diff --git a/include/mimalloc-types.h b/include/mimalloc-types.h
index cf142748..d44ecc18 100644
--- a/include/mimalloc-types.h
+++ b/include/mimalloc-types.h
@@ -374,8 +374,9 @@ typedef struct mi_segment_s {
 
   // layout like this to optimize access in `mi_free`
   mi_segment_kind_t kind;
-  _Atomic(mi_threadid_t) thread_id;      // unique id of the thread owning this segment
   size_t            slice_entries;       // entries in the `slices` array, at most `MI_SLICES_PER_SEGMENT`
+  _Atomic(mi_threadid_t) thread_id;      // unique id of the thread owning this segment
+
   mi_slice_t        slices[MI_SLICES_PER_SEGMENT+1];  // one more for huge blocks with large alignment
 } mi_segment_t;