diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index 8004ba84..1575c1fc 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -585,7 +585,11 @@ static inline bool mi_is_in_same_segment(const void* p, const void* q) {
 static inline bool mi_is_in_same_page(const void* p, const void* q) {
   mi_segment_t* segment = _mi_ptr_segment(p);
   if (_mi_ptr_segment(q) != segment) return false;
-  return (_mi_segment_page_of(segment, p) == _mi_segment_page_of(segment, q));
+  // assume q may be invalid // return (_mi_segment_page_of(segment, p) == _mi_segment_page_of(segment, q));
+  mi_page_t* page = _mi_segment_page_of(segment, p);
+  size_t psize;
+  uint8_t* start = _mi_segment_page_start(segment, page, &psize);
+  return (start <= (uint8_t*)q && (uint8_t*)q < start + psize);
 }
 
 static inline uintptr_t mi_rotl(uintptr_t x, uintptr_t shift) {