diff --git a/src/porting.h b/src/porting.h
index 6657d7bba..bf01c3e4d 100644
--- a/src/porting.h
+++ b/src/porting.h
@@ -89,11 +89,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #ifndef _WIN32 // POSIX
 	#include <sys/time.h>
 	#include <ctime>
-
-	#if defined(__MACH__) && defined(__APPLE__)
-		#include <mach/clock.h>
-		#include <mach/mach.h>
-	#endif
 #endif
 
 namespace porting
@@ -183,21 +178,16 @@ inline u64 getTimeNs() { return os_get_time(1000*1000*1000); }
 
 inline void os_get_clock(struct timespec *ts)
 {
-#if defined(__MACH__) && defined(__APPLE__)
-// From http://stackoverflow.com/questions/5167269/clock-gettime-alternative-in-mac-os-x
-// OS X does not have clock_gettime, use clock_get_time
-	clock_serv_t cclock;
-	mach_timespec_t mts;
-	host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);
-	clock_get_time(cclock, &mts);
-	mach_port_deallocate(mach_task_self(), cclock);
-	ts->tv_sec = mts.tv_sec;
-	ts->tv_nsec = mts.tv_nsec;
-#elif defined(CLOCK_MONOTONIC_RAW)
+#if defined(CLOCK_MONOTONIC_RAW)
 	clock_gettime(CLOCK_MONOTONIC_RAW, ts);
-#elif defined(_POSIX_MONOTONIC_CLOCK)
+#elif defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK > 0
 	clock_gettime(CLOCK_MONOTONIC, ts);
 #else
+# if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK == 0
+	// zero means it might be supported at runtime
+	if (clock_gettime(CLOCK_MONOTONIC, ts) == 0)
+		return;
+# endif
 	struct timeval tv;
 	gettimeofday(&tv, NULL);
 	TIMEVAL_TO_TIMESPEC(&tv, ts);