diff --git a/src/unix/bsd/freebsdlike/mod.rs b/src/unix/bsd/freebsdlike/mod.rs
index d7c99ee61f329ebc7688b2d5042e04565d5b11a1..d4b0fa74b26acc7d99ef227a70bb8b2c3573cc8f 100644
--- a/src/unix/bsd/freebsdlike/mod.rs
+++ b/src/unix/bsd/freebsdlike/mod.rs
@@ -160,6 +160,7 @@ pub const TMP_MAX: ::c_uint = 308915776;
 pub const O_RDONLY: ::c_int = 0;
 pub const O_WRONLY: ::c_int = 1;
 pub const O_RDWR: ::c_int = 2;
+pub const O_ACCMODE: ::c_int = 3;
 pub const O_APPEND: ::c_int = 8;
 pub const O_CREAT: ::c_int = 512;
 pub const O_EXCL: ::c_int = 2048;
diff --git a/src/unix/bsd/openbsdlike/mod.rs b/src/unix/bsd/openbsdlike/mod.rs
index b1bf2cafe16e66d469dbf26d7a7bb528698887f1..d4319b2d56294fedb6c153a40bc2851a74d3fca6 100644
--- a/src/unix/bsd/openbsdlike/mod.rs
+++ b/src/unix/bsd/openbsdlike/mod.rs
@@ -68,6 +68,7 @@ pub const L_tmpnam : ::c_uint = 1024;
 pub const O_RDONLY : ::c_int = 0;
 pub const O_WRONLY : ::c_int = 1;
 pub const O_RDWR : ::c_int = 2;
+pub const O_ACCMODE : ::c_int = 3;
 pub const O_APPEND : ::c_int = 8;
 pub const O_CREAT : ::c_int = 512;
 pub const O_EXCL : ::c_int = 2048;