diff --git a/libc/include/sys/mman.h b/libc/include/sys/mman.h
index 5a8c985..09bf0d9 100644
--- a/libc/include/sys/mman.h
+++ b/libc/include/sys/mman.h
@@ -54,7 +54,7 @@
 extern int munlockall(void);
 extern int mlock(const void*, size_t);
 extern int munlock(const void*, size_t);
-extern int madvise(const void*, size_t, int);
+extern int madvise(void*, size_t, int);
 
 extern int mlock(const void*, size_t);
 extern int munlock(const void*, size_t);