diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index ef554662..90afb72d 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -89,7 +89,7 @@ bool       _mi_os_unprotect(void* addr, size_t size);
 bool       _mi_os_commit(void* addr, size_t size, bool* is_zero, mi_stats_t* stats);
 bool       _mi_os_decommit(void* p, size_t size, mi_stats_t* stats);
 bool       _mi_os_reset(void* p, size_t size, mi_stats_t* stats);
-bool       _mi_os_unreset(void* p, size_t size, bool* is_zero, mi_stats_t* stats);
+// bool       _mi_os_unreset(void* p, size_t size, bool* is_zero, mi_stats_t* stats);
 size_t     _mi_os_good_alloc_size(size_t size);
 bool       _mi_os_has_overcommit(void);
 
diff --git a/include/mimalloc-types.h b/include/mimalloc-types.h
index d0d1b1d9..3487e628 100644
--- a/include/mimalloc-types.h
+++ b/include/mimalloc-types.h
@@ -178,21 +178,21 @@ typedef int32_t  mi_ssize_t;
 // Maximum number of size classes. (spaced exponentially in 12.5% increments)
 #define MI_BIN_HUGE  (73U)
 
-#if (MI_LARGE_OBJ_WSIZE_MAX >= 655360)
+#if (MI_MEDIUM_OBJ_WSIZE_MAX >= 655360)
 #error "mimalloc internal: define more bins"
 #endif
-#if (MI_ALIGNMENT_MAX > MI_SEGMENT_SIZE/2)
-#error "mimalloc internal: the max aligned boundary is too large for the segment size"
+#if (MI_ALIGNED_MAX % MI_SEGMENT_SLICE_SIZE != 0)
+#error "mimalloc internal: the max aligned boundary must be an integral multiple of the segment slice size"
 #endif
 
-// Maximum slice offset (7)
-#define MI_MAX_SLICE_OFFSET               ((MI_MEDIUM_PAGE_SIZE / MI_SEGMENT_SLICE_SIZE) - 1)
+// Maximum slice offset (15)
+#define MI_MAX_SLICE_OFFSET               ((MI_ALIGNMENT_MAX / MI_SEGMENT_SLICE_SIZE) - 1)
 
 // Used as a special value to encode block sizes in 32 bits.
 #define MI_HUGE_BLOCK_SIZE                ((uint32_t)MI_HUGE_OBJ_SIZE_MAX)
 
 // blocks up to this size are always allocated aligned
-#define MI_MAX_ALIGN_GUARANTEE  (8*MI_MAX_ALIGN_SIZE)  
+#define MI_MAX_ALIGN_GUARANTEE            (8*MI_MAX_ALIGN_SIZE)  
 
 
 
diff --git a/src/alloc-override-osx.c b/src/alloc-override-osx.c
index b53032e2..edd93b37 100644
--- a/src/alloc-override-osx.c
+++ b/src/alloc-override-osx.c
@@ -32,8 +32,7 @@ terms of the MIT license. A copy of the license can be found in the file
 extern "C" {
 #endif
 
-#if defined(MAC_OS_X_VERSION_10_6) && \
-    MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_6
+#if defined(MAC_OS_X_VERSION_10_6) && (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_6)
 // only available from OSX 10.6
 extern malloc_zone_t* malloc_default_purgeable_zone(void) __attribute__((weak_import));
 #endif
diff --git a/src/options.c b/src/options.c
index 72136978..24f51f80 100644
--- a/src/options.c
+++ b/src/options.c
@@ -72,7 +72,7 @@ static mi_option_desc_t options[_mi_option_last] =
   { 0, UNINIT, MI_OPTION(reset_decommits) },     // reset decommits memory
   #else
   { 1, UNINIT, MI_OPTION(eager_region_commit) },
-  { 0, UNINIT, MI_OPTION(reset_decommits) },     // reset uses MADV_FREE/MADV_DONTNEED
+  { 0, UNINIT, MI_OPTION(reset_decommits) },     // legacy; ignored now and reset always uses MADV_FREE/MADV_DONTNEED (issue #518)
   #endif
   { 0, UNINIT, MI_OPTION(large_os_pages) },      // use large OS pages, use only with eager commit to prevent fragmentation of VMA's
   { 0, UNINIT, MI_OPTION(reserve_huge_os_pages) },  // per 1GiB huge pages
diff --git a/src/os.c b/src/os.c
index 51ecdc5f..a7cc3cab 100644
--- a/src/os.c
+++ b/src/os.c
@@ -952,9 +952,12 @@ bool _mi_os_decommit(void* addr, size_t size, mi_stats_t* tld_stats) {
   return mi_os_commitx(addr, size, false, true /* conservative */, &is_zero, stats);
 }
 
+/*
 static bool mi_os_commit_unreset(void* addr, size_t size, bool* is_zero, mi_stats_t* stats) {  
-  return mi_os_commitx(addr, size, true, true /* conservative */, is_zero, stats);
+  return mi_os_commitx(addr, size, true, true // conservative
+                      , is_zero, stats);
 }
+*/
 
 // Signal to the OS that the address range is no longer in use
 // but may be used later again. This will release physical memory
@@ -1017,14 +1020,10 @@ static bool mi_os_resetx(void* addr, size_t size, bool reset, mi_stats_t* stats)
 bool _mi_os_reset(void* addr, size_t size, mi_stats_t* tld_stats) {
   MI_UNUSED(tld_stats);
   mi_stats_t* stats = &_mi_stats_main;
-  if (mi_option_is_enabled(mi_option_reset_decommits)) {
-    return _mi_os_decommit(addr, size, stats);
-  }
-  else {
-    return mi_os_resetx(addr, size, true, stats);
-  }
+  return mi_os_resetx(addr, size, true, stats);
 }
 
+/*
 bool _mi_os_unreset(void* addr, size_t size, bool* is_zero, mi_stats_t* tld_stats) {
   MI_UNUSED(tld_stats);
   mi_stats_t* stats = &_mi_stats_main;
@@ -1036,7 +1035,7 @@ bool _mi_os_unreset(void* addr, size_t size, bool* is_zero, mi_stats_t* tld_stat
     return mi_os_resetx(addr, size, false, stats);
   }
 }
-
+*/
 
 // Protect a region in memory to be not accessible.
 static  bool mi_os_protectx(void* addr, size_t size, bool protect) {
diff --git a/src/segment.c b/src/segment.c
index 7b2fa28e..3001f160 100644
--- a/src/segment.c
+++ b/src/segment.c
@@ -317,7 +317,7 @@ static uint8_t* _mi_segment_page_start_from_slice(const mi_segment_t* segment, c
   size_t psize = (size_t)slice->slice_count * MI_SEGMENT_SLICE_SIZE;
   // make the start not OS page aligned for smaller blocks to avoid page/cache effects
   size_t start_offset = (xblock_size >= MI_INTPTR_SIZE && xblock_size <= 1024 ? MI_MAX_ALIGN_GUARANTEE : 0); 
-  if (page_size != NULL) *page_size = psize - start_offset;
+  if (page_size != NULL) { *page_size = psize - start_offset; }
   return (uint8_t*)segment + ((idx*MI_SEGMENT_SLICE_SIZE) + start_offset);
 }