diff --git a/include/mimalloc/internal.h b/include/mimalloc/internal.h
index e175f331..535fe1fb 100644
--- a/include/mimalloc/internal.h
+++ b/include/mimalloc/internal.h
@@ -67,8 +67,8 @@ terms of the MIT license. A copy of the license can be found in the file
 
 // "libc.c"
 #include <stdarg.h>
-void          _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args);
-void          _mi_snprintf(char* buf, size_t buflen, const char* fmt, ...);
+int           _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args);
+int           _mi_snprintf(char* buf, size_t buflen, const char* fmt, ...);
 char          _mi_toupper(char c);
 int           _mi_strnicmp(const char* s, const char* t, size_t n);
 void          _mi_strlcpy(char* dest, const char* src, size_t dest_size);
diff --git a/src/libc.c b/src/libc.c
index a0eeca17..b18dff2c 100644
--- a/src/libc.c
+++ b/src/libc.c
@@ -84,8 +84,8 @@ bool _mi_getenv(const char* name, char* result, size_t result_size) {
 // This is mostly to avoid calling these when libc is not yet
 // initialized (and to reduce dependencies)
 //
-// format:      d i, p, x, u, s
-// type:        z l ll L
+// format:      d i, p x u, s
+// prec:        z l ll L
 // width:       10
 // align-left:  -
 // fill:        0
@@ -160,8 +160,8 @@ static void mi_out_num(uintmax_t x, size_t base, char prefix, char** out, char*
 
 #define MI_NEXTC()  c = *in; if (c==0) break; in++;
 
-void _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args) {
-  if (buf == NULL || bufsize == 0 || fmt == NULL) return;
+int _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args) {
+  if (buf == NULL || bufsize == 0 || fmt == NULL) return 0;
   buf[bufsize - 1] = 0;
   char* const end = buf + (bufsize - 1);
   const char* in = fmt;
@@ -279,13 +279,15 @@ void _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args) {
   }
   mi_assert_internal(out <= end);
   *out = 0;
+  return (int)(out - buf);
 }
 
-void _mi_snprintf(char* buf, size_t buflen, const char* fmt, ...) {
+int _mi_snprintf(char* buf, size_t buflen, const char* fmt, ...) {
   va_list args;
   va_start(args, fmt);
-  _mi_vsnprintf(buf, buflen, fmt, args);
+  const int written = _mi_vsnprintf(buf, buflen, fmt, args);
   va_end(args);
+  return written;
 }
 
 
diff --git a/src/page.c b/src/page.c
index 0732665b..2af89c66 100644
--- a/src/page.c
+++ b/src/page.c
@@ -253,7 +253,7 @@ void _mi_page_abandon(mi_page_t* page, mi_page_queue_t* pq) {
     mi_page_queue_remove(pq, page);
     mi_tld_t* tld = page->heap->tld;
     mi_page_set_heap(page, NULL);
-    _mi_arenas_page_abandon(page);  
+    _mi_arenas_page_abandon(page);
     _mi_arenas_collect(false, false, tld); // allow purging
   }
 }
@@ -265,7 +265,7 @@ static mi_page_t* mi_page_fresh_alloc(mi_heap_t* heap, mi_page_queue_t* pq, size
   mi_assert_internal(pq != NULL);
   mi_assert_internal(mi_heap_contains_queue(heap, pq));
   mi_assert_internal(page_alignment > 0 || block_size > MI_LARGE_MAX_OBJ_SIZE || block_size == pq->block_size);
-  #endif  
+  #endif
   mi_page_t* page = _mi_arenas_page_alloc(heap, block_size, page_alignment);
   if (page == NULL) {
     // out-of-memory
@@ -612,7 +612,7 @@ static void mi_page_extend_free(mi_heap_t* heap, mi_page_t* page) {
   if (page->slice_committed > 0) {
     const size_t needed_size = (page->capacity + extend)*bsize;
     const size_t needed_commit = _mi_align_up( mi_page_slice_offset_of(page, needed_size), MI_PAGE_MIN_COMMIT_SIZE );
-    if (needed_commit > page->slice_committed) {      
+    if (needed_commit > page->slice_committed) {
       mi_assert_internal(((needed_commit - page->slice_committed) % _mi_os_page_size()) == 0);
       _mi_os_commit(mi_page_slice_start(page) + page->slice_committed, needed_commit - page->slice_committed, NULL);
       page->slice_committed = needed_commit;
@@ -957,7 +957,6 @@ void* _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero, size_t huge_al
   }
   // move singleton pages to the full queue
   if (page->reserved == page->used) {
-    mi_assert_internal(page->reserved == 1);
     mi_page_to_full(page, mi_page_queue_of(page));
   }
   return p;