diff --git a/dev/ci/nix/default.nix b/dev/ci/nix/default.nix
index 05624ff4a1..741cb89eed 100644
--- a/dev/ci/nix/default.nix
+++ b/dev/ci/nix/default.nix
@@ -114,6 +114,7 @@ let projects = {
   mtac2 = callPackage ./mtac2.nix {};
   oddorder = callPackage ./oddorder.nix {};
   quickchick = callPackage ./quickchick.nix {};
+  simple-io = callPackage ./simple-io.nix {};
   verdi-raft = callPackage ./verdi-raft.nix {};
   VST = callPackage ./VST.nix {};
 }; in
diff --git a/dev/ci/nix/simple-io.nix b/dev/ci/nix/simple-io.nix
new file mode 100644
index 0000000000..3b7b6c09b1
--- /dev/null
+++ b/dev/ci/nix/simple-io.nix
@@ -0,0 +1,5 @@
+{ ocamlPackages, ssreflect, coq-ext-lib, simple-io }:
+{
+  buildInputs = with ocamlPackages; [ ocaml findlib ocamlbuild num ];
+  coqBuildInputs = [ ssreflect coq-ext-lib ];
+}