--- Libc/Libc-583/sys/munmap.c
+++ Libc/Libc-391.4.1/sys/munmap.c
@@ -23,20 +23,21 @@
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/mman.h>
+#include <sys/syscall.h>
 
 /*
  * Stub function to account for the differences in standard compliance
  * while maintaining binary backward compatibility.
- *
- * This is only the legacy behavior.
  */
-extern int __munmap(void *, size_t);
-
 int
 munmap(void *addr, size_t len)
 {
+#if __DARWIN_UNIX03
+	return syscall(SYS_munmap, addr, len);
+#else	/* !__DARWIN_UNIX03 */
 	int	page_mask;
 	size_t	offset;
+	int	rv;
 
 	if (len == 0) {
 		/*
@@ -55,5 +56,7 @@
 	offset = ((uintptr_t) addr) & page_mask;
 	addr = (void *) (((uintptr_t) addr) & ~page_mask);
 	len += offset;
-	return __munmap(addr, len);
+	rv = syscall(SYS_munmap, addr, len);
+	return rv;
+#endif	/* !__DARWIN_UNIX03 */
 }