diff --git a/include/mimalloc/bits.h b/include/mimalloc/bits.h
index 5b847f4b..64875e9d 100644
--- a/include/mimalloc/bits.h
+++ b/include/mimalloc/bits.h
@@ -205,9 +205,8 @@ static inline size_t mi_ctz(size_t x) {
   #elif mi_has_builtinz(ctz)
     return (x!=0 ? (size_t)mi_builtinz(ctz)(x) : MI_SIZE_BITS);
   #elif defined(__GNUC__) && (MI_ARCH_X64 || MI_ARCH_X86)
-    if (x==0) return MI_SIZE_BITS;
-    size_t r;
-    __asm ("bsf\t%1, %0" : "=r"(r) : "r"(x) : "cc");
+    size_t r = MI_SIZE_BITS;  // bsf leaves destination unmodified if the argument is 0 (see <https://github.com/llvm/llvm-project/pull/102885>)
+    __asm ("bsf\t%1, %0" : "+r"(r) : "r"(x) : "cc");
     return r;
   #elif MI_HAS_FAST_POPCOUNT
     return (x!=0 ? (mi_popcount(x^(x-1))-1) : MI_SIZE_BITS);
diff --git a/include/mimalloc/internal.h b/include/mimalloc/internal.h
index d96cfa4c..01373025 100644
--- a/include/mimalloc/internal.h
+++ b/include/mimalloc/internal.h
@@ -789,7 +789,7 @@ 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));
+  // mi_assert_internal(!mi_page_is_in_full(page));  // can happen when destroying pages on heap_destroy
   // 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;