diff --git a/libc/include/sys/mman.h b/libc/include/sys/mman.h
index 7a32974..7c5f8d7 100644
--- a/libc/include/sys/mman.h
+++ b/libc/include/sys/mman.h
@@ -45,6 +45,7 @@
 #define MREMAP_FIXED    2
 
 extern void*  mmap(void *, size_t, int, int, int, off_t);
+extern void*  mmap64(void *, size_t, int, int, int, off64_t);
 extern int    munmap(void *, size_t);
 extern int    msync(const void *, size_t, int);
 extern int    mprotect(const void *, size_t, int);