diff --git a/include/mimalloc/internal.h b/include/mimalloc/internal.h
index e43d4420..d96cfa4c 100644
--- a/include/mimalloc/internal.h
+++ b/include/mimalloc/internal.h
@@ -790,11 +790,12 @@ static inline void mi_page_set_has_aligned(mi_page_t* page, bool has_aligned) {
 
 static inline void mi_page_set_heap(mi_page_t* page, mi_heap_t* heap) {
   mi_assert_internal(!mi_page_is_in_full(page));
-  const mi_page_flags_t flags = mi_page_flags(page);
-  const mi_threadid_t tid = (heap != NULL ? heap->tld->thread_id : 0) | flags;  // for MI_PAGE_HAS_ALIGNED
+  // only the aligned flag is retained (and in particular clear the abandoned-mapped flag).
+  const mi_page_flags_t flags = (mi_page_has_aligned(page) ? MI_PAGE_HAS_ALIGNED : 0);
+  const mi_threadid_t tid = (heap == NULL ? 0 : heap->tld->thread_id) | flags;
   if (heap != NULL) {
     page->heap = heap;
-    page->heap_tag = heap->tag;
+    page->heap_tag = heap->tag;    
   }
   else {
     page->heap = NULL;