diff --git a/src/lib.rs b/src/lib.rs
index aa7889ef8e..98748f90c9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -160,6 +160,10 @@ pub mod flag {
     pub const PROT_READ: u32 = libc::PROT_READ as u32;
     pub const PROT_WRITE: u32 = libc::PROT_WRITE as u32;
     pub const PROT_EXEC: u32 = libc::PROT_EXEC as u32;
+
+    pub const WNOHANG: u32 = libc::WNOHANG as u32;
+    pub const WUNTRACED: u32 = libc::WUNTRACED as u32;
+    pub const WCONTINUED: u32 = libc::WCONTINUED as u32;
 }
 
 pub mod errno {