diff --git a/configure.ac b/configure.ac
index a5b49d9a1..676aa42ca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -223,6 +223,10 @@ AC_CHECK_HEADERS([execinfo.h])
 if test "$my_htop_platform" = darwin; then
    AC_CHECK_HEADERS([mach/mach_time.h])
    AC_CHECK_TYPES([thread_extended_info_data_t], [], [], [[#include <mach/thread_info.h>]])
+   AC_CHECK_MEMBERS([struct vm_statistics64.compressor_page_count], [], [], [[#include <mach/mach_host.h>]])
+   AC_CHECK_MEMBERS([struct vm_statistics64.external_page_count], [], [], [[#include <mach/mach_host.h>]])
+
+   AC_CHECK_DECLS([kIOMainPortDefault], [], [], [[#include <IOKit/IOKitLib.h>]])
 fi
 
 # ----------------------------------------------------------------------
diff --git a/darwin/DarwinMachine.c b/darwin/DarwinMachine.c
index 4937be105..df50f2303 100644
--- a/darwin/DarwinMachine.c
+++ b/darwin/DarwinMachine.c
@@ -16,6 +16,7 @@ in the source distribution for its full text.
 #include <unistd.h>
 #include <sys/mman.h>
 #include <sys/sysctl.h>
+#include <Availability.h>
 
 #include "CRT.h"
 #include "Machine.h"
@@ -24,6 +25,10 @@ in the source distribution for its full text.
 #include "generic/openzfs_sysctl.h"
 #include "zfs/ZfsArcStats.h"
 
+// Compatibility for older SDKs.
+#if defined(HAVE_DECL_KIOMAINPORTDEFAULT) && !HAVE_DECL_KIOMAINPORTDEFAULT
+#define kIOMainPortDefault kIOMasterPortDefault
+#endif
 
 static void DarwinMachine_getHostInfo(host_basic_info_data_t* p) {
    mach_msg_type_number_t info_size = HOST_BASIC_INFO_COUNT;
diff --git a/darwin/Platform.c b/darwin/Platform.c
index 72d262590..b871fc5aa 100644
--- a/darwin/Platform.c
+++ b/darwin/Platform.c
@@ -15,11 +15,11 @@ in the source distribution for its full text.
 #include <math.h>
 #include <stdlib.h>
 #include <unistd.h>
-#include <net/if.h>
 #include <net/if_types.h>
 #include <net/route.h>
 #include <sys/socket.h>
 #include <mach/port.h>
+#include <net/if.h> // After `sys/socket.h` for struct `sockaddr` (for iOS6 SDK)
 
 #include <CoreFoundation/CFBase.h>
 #include <CoreFoundation/CFDictionary.h>
@@ -404,15 +404,26 @@ void Platform_setMemoryValues(Meter* mtr) {
    mtr->total = dhost->host_info.max_mem / 1024;
 #ifdef HAVE_STRUCT_VM_STATISTICS64
    natural_t used = vm->active_count + vm->inactive_count +
-              vm->speculative_count + vm->wire_count +
-              vm->compressor_page_count - vm->purgeable_count - vm->external_page_count;
+              vm->speculative_count + vm->wire_count - vm->purgeable_count;
+#ifdef HAVE_STRUCT_VM_STATISTICS64_EXTERNAL_PAGE_COUNT
+   used -= vm->external_page_count;
+#endif
+#ifdef HAVE_STRUCT_VM_STATISTICS64_COMPRESSOR_PAGE_COUNT
+   used += vm->compressor_page_count;
    mtr->values[MEMORY_METER_USED] = (double)(used - vm->compressor_page_count) * page_K;
+#else
+   mtr->values[MEMORY_METER_USED] = (double)used * page_K;
+#endif
 #else
    mtr->values[MEMORY_METER_USED] = (double)(vm->active_count + vm->wire_count) * page_K;
 #endif
    // mtr->values[MEMORY_METER_SHARED] = "shared memory, like tmpfs and shm"
 #ifdef HAVE_STRUCT_VM_STATISTICS64
+#ifdef HAVE_STRUCT_VM_STATISTICS64_COMPRESSOR_PAGE_COUNT
    mtr->values[MEMORY_METER_COMPRESSED] = (double)vm->compressor_page_count * page_K;
+#else
+   // mtr->values[MEMORY_METER_COMPRESSED] = "compressed memory not available"
+#endif
 #else
    // mtr->values[MEMORY_METER_COMPRESSED] = "compressed memory, like zswap on linux"
 #endif