--- a/source/syscalls.h
+++ b/source/syscalls.h
@@ -20,12 +20,6 @@
 # endif
 #endif
 
-// This check is way underinclusive.
-#if !defined(TARGET_OS_LINUX) && !defined(TARGET_OS_WINDOWS) && !defined(TARGET_OS_NETBSD) && !defined(TARGET_OS_SOLARIS)
-# define NEED_FAKE_FDATASYNC
-int fdatasync(int fd);
-#endif
-
 #ifdef NEED_USLEEP
 void usleep(unsigned long time);
 #endif
