diff --git a/include/mimalloc/bits.h b/include/mimalloc/bits.h
index ca0b5905..ed4a7b44 100644
--- a/include/mimalloc/bits.h
+++ b/include/mimalloc/bits.h
@@ -107,6 +107,7 @@ typedef int32_t  mi_ssize_t;
 // Define big endian if needed
 // #define MI_BIG_ENDIAN  1
 
+// maximum virtual address bits in a user-space pointer
 #if MI_DEFAULT_VIRTUAL_ADDRESS_BITS > 0 
 #define MI_MAX_VABITS     MI_DEFAULT_VIRTUAL_ADDRESS_BITS
 #elif   MI_ARCH_X64
@@ -117,6 +118,7 @@ typedef int32_t  mi_ssize_t;
 #define MI_MAX_VABITS     (32)
 #endif
 
+// use a flat page-map (or a 2-level one)
 #ifndef MI_PAGE_MAP_FLAT
 #if MI_MAX_VABITS <= 40
 #define MI_PAGE_MAP_FLAT  1
diff --git a/src/arena-meta.c b/src/arena-meta.c
index 065a1331..fcfb680c 100644
--- a/src/arena-meta.c
+++ b/src/arena-meta.c
@@ -25,7 +25,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #define MI_META_PAGE_SIZE         MI_ARENA_SLICE_SIZE
 #define MI_META_PAGE_ALIGN        MI_ARENA_SLICE_ALIGN
 
-#define MI_META_BLOCK_SIZE        (64)
+#define MI_META_BLOCK_SIZE        (128)                       // large enough such that META_MAX_SIZE > 4k (even on 32-bit)
 #define MI_META_BLOCK_ALIGN       MI_META_BLOCK_SIZE
 #define MI_META_BLOCKS_PER_PAGE   (MI_ARENA_SLICE_SIZE / MI_META_BLOCK_SIZE)  // 1024
 #define MI_META_MAX_SIZE          (MI_BCHUNK_SIZE * MI_META_BLOCK_SIZE)
diff --git a/src/page-map.c b/src/page-map.c
index 5a25b839..190be6c0 100644
--- a/src/page-map.c
+++ b/src/page-map.c
@@ -147,7 +147,7 @@ void _mi_page_map_unregister_range(void* start, size_t size) {
 mi_page_t* _mi_safe_ptr_page(const void* p) {
   if mi_unlikely(p >= mi_page_map_max_address) return NULL;
   const uintptr_t idx = _mi_page_map_index(p);
-  if mi_unlikely(mi_page_map_commit == NULL || !mi_bitmap_is_set(mi_page_map_commit, idx/MI_PAGE_MAP_ENTRIES_PER_COMMIT_BIT)) return NULL;
+  if mi_unlikely(mi_page_map_commit != NULL && !mi_bitmap_is_set(mi_page_map_commit, idx/MI_PAGE_MAP_ENTRIES_PER_COMMIT_BIT)) return NULL;
   const uintptr_t ofs = _mi_page_map[idx];
   if mi_unlikely(ofs == 0) return NULL;
   return (mi_page_t*)((((uintptr_t)p >> MI_ARENA_SLICE_SHIFT) - ofs + 1) << MI_ARENA_SLICE_SHIFT);