diff --git a/port/port_posix.h b/port/port_posix.h
index f2b89bffb99c2..21c845e211ff0 100644
--- a/port/port_posix.h
+++ b/port/port_posix.h
@@ -62,12 +62,16 @@
 #define fflush_unlocked fflush
 #endif
 
-#if defined(OS_MACOSX) || defined(OS_FREEBSD) ||\
+#if defined(OS_FREEBSD) ||\
     defined(OS_OPENBSD) || defined(OS_DRAGONFLYBSD)
 // Use fsync() on platforms without fdatasync()
 #define fdatasync fsync
 #endif
 
+#if defined(OS_MACOSX)
+#define fdatasync(fd) fcntl(fd, F_FULLFSYNC, 0)
+#endif
+
 #if defined(OS_ANDROID) && __ANDROID_API__ < 9
 // fdatasync() was only introduced in API level 9 on Android. Use fsync()
 // when targetting older platforms.