diff --git a/src/flag.rs b/src/flag.rs
index 5351384..52db74c 100644
--- a/src/flag.rs
+++ b/src/flag.rs
@@ -41,3 +41,5 @@ pub const O_FSYNC: usize = 0x80;
 pub const O_CREAT: usize = 0x200;
 pub const O_TRUNC: usize = 0x400;
 pub const O_EXCL: usize = 0x800;
+
+pub const WNOHANG: usize = 1;