diff --git a/.ocamlformat b/.ocamlformat
index f146225..c365faf 100644
--- a/.ocamlformat
+++ b/.ocamlformat
@@ -1,4 +1,4 @@
-version=0.26.2
+version=0.27.0
 assignment-operator=end-line
 break-cases=fit
 break-fun-decl=wrap
diff --git a/CHANGES.md b/CHANGES.md
index 7567c4a..52c2497 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,7 @@
 ## unreleased
 
+- add some signals stuff to `Sys` module
+
 ## 0.3 - 2024-07-26
 
 - move monoporphic comparison operators to Infix submodule
diff --git a/src/prelude.ml b/src/prelude.ml
index d930604..b16163d 100644
--- a/src/prelude.ml
+++ b/src/prelude.ml
@@ -112,6 +112,71 @@ module Stdlib = Empty
 
 (* Use Bos instead. *)
 module Sys = struct
+  (* Signals *)
+  type signal_behavior = Sys.signal_behavior =
+    | Signal_default
+    | Signal_ignore
+    | Signal_handle of (int -> unit)
+
+  let set_signal = Sys.set_signal
+
+  let sigabrt = Sys.sigabrt
+
+  let sigalrm = Sys.sigalrm
+
+  let sigfpe = Sys.sigfpe
+
+  let sighup = Sys.sighup
+
+  let sigill = Sys.sigill
+
+  let sigint = Sys.sigint
+
+  let sigkill = Sys.sigkill
+
+  let sigpipe = Sys.sigpipe
+
+  let sigquit = Sys.sigquit
+
+  let sigsegv = Sys.sigsegv
+
+  let sigterm = Sys.sigterm
+
+  let sigusr1 = Sys.sigusr1
+
+  let sigusr2 = Sys.sigusr2
+
+  let sigchld = Sys.sigchld
+
+  let sigcont = Sys.sigcont
+
+  let sigstop = Sys.sigstop
+
+  let sigtstp = Sys.sigtstp
+
+  let sigttin = Sys.sigttin
+
+  let sigttou = Sys.sigttou
+
+  let sigvtalrm = Sys.sigvtalrm
+
+  let sigprof = Sys.sigprof
+
+  let sigbus = Sys.sigbus
+
+  let sigpoll = Sys.sigpoll
+
+  let sigsys = Sys.sigsys
+
+  let sigtrap = Sys.sigtrap
+
+  let sigurg = Sys.sigurg
+
+  let sigxcpu = Sys.sigxcpu
+
+  let sigxfsz = Sys.sigxfsz
+
+  (* Other stuff *)
   let opaque_identity = Sys.opaque_identity
 end