diff --git a/libc/include/sys/swap.h b/libc/include/sys/swap.h
index 97a6f36..e4c1819 100644
--- a/libc/include/sys/swap.h
+++ b/libc/include/sys/swap.h
@@ -33,6 +33,11 @@
 
 __BEGIN_DECLS
 
+#define SWAP_FLAG_DISCARD 0x10000
+#define SWAP_FLAG_PREFER 0x8000
+#define SWAP_FLAG_PRIO_MASK 0x7fff
+#define SWAP_FLAG_PRIO_SHIFT 0
+
 extern int swapon(const char*, int) __nonnull((1));
 extern int swapoff(const char*) __nonnull((1));