diff --git a/nix/alt-ergo.nix b/nix/alt-ergo.nix
index 3b3965b10d1d6a5e41a2e5fbd781249863730d16..5dd4049507f1fc5a1a692ca6948768443fb16a86 100644
--- a/nix/alt-ergo.nix
+++ b/nix/alt-ergo.nix
@@ -22,7 +22,7 @@ stdenv.mkDerivation rec {
   src = fetchFromGitHub {
     owner = "OCamlPro";
     repo = pname;
-    rev = version;
+    rev = "refs/tags/"+version;
     sha256 = "11ffm87vsrii8nyhxhbc9gzjmqkspqv7hpjq7ll9xflll7gpnpkj";
   };