diff --git a/src/ipv4/ipv4_wire.ml b/src/ipv4/ipv4_wire.ml
index 495505b8..cbc869c4 100644
--- a/src/ipv4/ipv4_wire.ml
+++ b/src/ipv4/ipv4_wire.ml
@@ -1,7 +1,7 @@
 let sizeof_ipv4 = 20
 
 let hlen_version_off = 0
-let _tos_off = 1
+let tos_off = 1
 let len_off = 2
 let id_off = 4
 let off_off = 6
@@ -14,6 +14,9 @@ let dst_off = 16
 let get_hlen_version buf = Cstruct.get_uint8 buf hlen_version_off
 let set_hlen_version buf v = Cstruct.set_uint8 buf hlen_version_off v
 
+let get_tos buf = Cstruct.get_uint8 buf tos_off
+let set_tos buf v = Cstruct.set_uint8 buf tos_off v
+
 let get_len buf = Cstruct.BE.get_uint16 buf len_off
 let set_len buf v = Cstruct.BE.set_uint16 buf len_off v
 
diff --git a/src/ipv4/ipv4_wire.mli b/src/ipv4/ipv4_wire.mli
index df055d7f..0e29ee50 100644
--- a/src/ipv4/ipv4_wire.mli
+++ b/src/ipv4/ipv4_wire.mli
@@ -3,6 +3,9 @@ val sizeof_ipv4 : int
 val get_hlen_version : Cstruct.t -> int
 val set_hlen_version : Cstruct.t -> int -> unit
 
+val get_tos : Cstruct.t -> int
+val set_tos : Cstruct.t -> int -> unit
+
 val get_len : Cstruct.t -> int
 val set_len : Cstruct.t -> int -> unit