diff --git a/dlls/ntdll/virtual.c b/dlls/ntdll/virtual.c
index bacfa32e475..6ce53312624 100644
--- a/dlls/ntdll/virtual.c
+++ b/dlls/ntdll/virtual.c
@@ -1681,14 +1681,16 @@ void virtual_release_address_space( BOOL free_high_mem )
 
     server_enter_uninterrupted_section( &csVirtual, &sigset );
 
+#ifndef __APPLE__  /* dyld doesn't support parts of the WINE_DOS segment being unmapped */
     range.base  = (char *)0x20000000;
     range.limit = (char *)0x7f000000;
     while (wine_mmap_enum_reserved_areas( free_reserved_memory, &range, 0 )) /* nothing */;
+#endif
 
     /* no large address space on win9x */
     if (free_high_mem && NtCurrentTeb()->Peb->OSPlatformId == VER_PLATFORM_WIN32_NT)
     {
-        range.base  = (char *)0x80000000;
+        range.base  = (char *)0x82000000;
         range.limit = address_space_limit;
         while (wine_mmap_enum_reserved_areas( free_reserved_memory, &range, 1 )) /* nothing */;
         user_space_limit = working_set_limit = address_space_limit;
diff --git a/loader/main.c b/loader/main.c
index 676eae3cdb6..e0588d11993 100644
--- a/loader/main.c
+++ b/loader/main.c
@@ -40,9 +40,9 @@
 
 #ifdef __APPLE__
 
-asm(".zerofill WINE_DOS, WINE_DOS, ___wine_dos, 0x70000000");
+asm(".zerofill WINE_DOS, WINE_DOS, ___wine_dos, 0x40000000");
 asm(".zerofill WINE_SHAREDHEAP, WINE_SHAREDHEAP, ___wine_shared_heap, 0x03000000");
-extern char __wine_dos[0x70000000], __wine_shared_heap[0x03000000];
+extern char __wine_dos[0x40000000], __wine_shared_heap[0x03000000];
 
 static const struct wine_preload_info wine_main_preload_info[] =
 {