diff --git a/.github/workflows/nix-action-coq-8.20.yml b/.github/workflows/nix-action-coq-8.20.yml
index 678ad2fb2..8ff06daeb 100644
--- a/.github/workflows/nix-action-coq-8.20.yml
+++ b/.github/workflows/nix-action-coq-8.20.yml
@@ -53,9 +53,9 @@ jobs:
       run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "coq-8.20"
         --argstr job "mathcomp-ssreflect"
     - if: steps.stepCheck.outputs.status == 'built'
-      name: 'Building/fetching previous CI target: coq-ext-lib'
+      name: 'Building/fetching previous CI target: ExtLib'
       run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "coq-8.20"
-        --argstr job "coq-ext-lib"
+        --argstr job "ExtLib"
     - if: steps.stepCheck.outputs.status == 'built'
       name: 'Building/fetching previous CI target: simple-io'
       run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "coq-8.20"
diff --git a/.nix/config.nix b/.nix/config.nix
index 847b0e0cd..3958ebf7f 100644
--- a/.nix/config.nix
+++ b/.nix/config.nix
@@ -31,9 +31,6 @@ let master = [
       coqPackages = common-bundles // {
         coq.override.version = "8.20";
       };
-      ocamlPackages = {
-        elpi.override.version = "v2.0.3";
-      };
     };
 
     "coq-master" = {
diff --git a/.nix/coq-nix-toolbox.nix b/.nix/coq-nix-toolbox.nix
index 57c8d2bdf..76a268d4a 100644
--- a/.nix/coq-nix-toolbox.nix
+++ b/.nix/coq-nix-toolbox.nix
@@ -1 +1 @@
-"7ff53c990ee876ed8aa55361cbf30a163702a13d"
+"858ff8dd010deded3b9cab8e04fbfad20151af5c"
diff --git a/.nix/coq-overlays/coq-elpi/default.nix b/.nix/coq-overlays/coq-elpi/default.nix
new file mode 100644
index 000000000..96b4b5d68
--- /dev/null
+++ b/.nix/coq-overlays/coq-elpi/default.nix
@@ -0,0 +1,86 @@
+{ lib, mkCoqDerivation, which, coq, version ? null }:
+
+let
+  elpi = coq.ocamlPackages.elpi.override (lib.switch coq.coq-version [
+    { case = "8.11"; out = { version = "1.11.4"; };}
+    { case = "8.12"; out = { version = "1.12.0"; };}
+    { case = "8.13"; out = { version = "1.13.7"; };}
+    { case = "8.14"; out = { version = "1.13.7"; };}
+    { case = "8.15"; out = { version = "1.15.0"; };}
+    { case = "8.16"; out = { version = "1.17.0"; };}
+    { case = "8.17"; out = { version = "1.17.0"; };}
+    { case = "8.18"; out = { version = "1.18.1"; };}
+    { case = "8.19"; out = { version = "1.18.1"; };}
+    { case = "8.20"; out = { version = "2.0.3"; };}
+  ] {} );
+in (mkCoqDerivation {
+  pname = "elpi";
+  repo  = "coq-elpi";
+  owner = "LPCIC";
+  inherit version;
+  defaultVersion = lib.switch coq.coq-version [
+    { case = "8.20"; out = "2.2.0"; }
+    { case = "8.19"; out = "2.0.1"; }
+    { case = "8.18"; out = "2.0.0"; }
+    { case = "8.17"; out = "1.18.0"; }
+    { case = "8.16"; out = "1.15.6"; }
+    { case = "8.15"; out = "1.14.0"; }
+    { case = "8.14"; out = "1.11.2"; }
+    { case = "8.13"; out = "1.11.1"; }
+    { case = "8.12"; out = "1.8.3_8.12"; }
+    { case = "8.11"; out = "1.6.3_8.11"; }
+  ] null;
+  release."2.2.0".sha256      = "sha256-rADEoqTXM7/TyYkUKsmCFfj6fjpWdnZEOK++5oLfC/I=";
+  release."2.0.1".sha256      = "sha256-cuoPsEJ+JRLVc9Golt2rJj4P7lKltTrrmQijjoViooc=";
+  release."2.0.0".sha256      = "sha256-A/cH324M21k3SZ7+YWXtaYEbu6dZQq3K0cb1RMKjbsM=";
+  release."1.19.0".sha256     = "sha256-kGoo61nJxeG/BqV+iQaV3iinwPStND+7+fYMxFkiKrQ=";
+  release."1.18.0".sha256     = "sha256-2fCOlhqi4YkiL5n8SYHuc3pLH+DArf9zuMH7IhpBc2Y=";
+  release."1.17.0".sha256     = "sha256-J8GatRKFU0ekNCG3V5dBI+FXypeHcLgC5QJYGYzFiEM=";
+  release."1.15.6".sha256     = "sha256-qc0q01tW8NVm83801HHOBHe/7H1/F2WGDbKO6nCXfno=";
+  release."1.15.1".sha256     = "sha256-NT2RlcIsFB9AvBhMxil4ZZIgx+KusMqDflj2HgQxsZg=";
+  release."1.14.0".sha256     = "sha256:1v2p5dlpviwzky2i14cj7gcgf8cr0j54bdm9fl5iz1ckx60j6nvp";
+  release."1.13.0".sha256     = "1j7s7dlnjbw222gnbrsjgmjck1yrx7h6hwm8zikcyxi0zys17w7n";
+  release."1.12.1".sha256     = "sha256-4mO6/co7NcIQSGIQJyoO8lNWXr6dqz+bIYPO/G0cPkY=";
+  release."1.11.2".sha256     = "0qk5cfh15y2zrja7267629dybd3irvxk1raz7z8qfir25a81ckd4";
+  release."1.11.1".sha256     = "10j076vc2hdcbm15m6s7b6xdzibgfcbzlkgjnlkr2vv9k13qf8kc";
+  release."1.10.1".sha256     = "1zsyx26dvj7pznfd2msl2w7zbw51q1nsdw0bdvdha6dga7ijf7xk";
+  release."1.9.7".sha256      = "0rvn12h9dpk9s4pxy32p8j0a1h7ib7kg98iv1cbrdg25y5vs85n1";
+  release."1.9.5".sha256      = "0gjdwmb6bvb5gh0a6ra48bz5fb3pr5kpxijb7a8mfydvar5i9qr6";
+  release."1.9.4".sha256      = "0nii7238mya74f9g6147qmpg6gv6ic9b54x5v85nb6q60d9jh0jq";
+  release."1.9.3".sha256      = "198irm800fx3n8n56vx1c6f626cizp1d7jfkrc6ba4iqhb62ma0z";
+  release."1.9.2".sha256      = "1rr2fr8vjkc0is7vh1461aidz2iwkigdkp6bqss4hhv0c3ijnn07";
+  release."1.8.3_8.12".sha256  = "15z2l4zy0qpw0ws7bvsmpmyv543aqghrfnl48nlwzn9q0v89p557";
+  release."1.8.3_8.12".version = "1.8.3";
+  release."1.8.2_8.12".sha256  = "1n6jwcdazvjgj8vsv2r9zgwpw5yqr5a1ndc2pwhmhqfl04b5dk4y";
+  release."1.8.2_8.12".version = "1.8.2";
+  release."1.8.1".sha256      = "1fbbdccdmr8g4wwpihzp4r2xacynjznf817lhijw6kqfav75zd0r";
+  release."1.8.0".sha256      = "13ywjg94zkbki22hx7s4gfm9rr87r4ghsgan23xyl3l9z8q0idd1";
+  release."1.7.0".sha256      = "1ws5cqr0xawv69prgygbl3q6dgglbaw0vc397h9flh90kxaqgyh8";
+  release."1.6.3_8.11".sha256 = "1j340cr2bv95clzzkkfmsjkklham1mj84cmiyprzwv20q89zr1hp";
+  release."1.6.3_8.11".version = "1.6.3";
+  release."1.6.2_8.11".sha256 = "06xrx0ljilwp63ik2sxxr7h617dgbch042xfcnfpy5x96br147rn";
+  release."1.6.2_8.11".version = "1.6.2";
+  release."1.6.1_8.11".sha256 = "0yyyh35i1nb3pg4hw7cak15kj4y6y9l84nwar9k1ifdsagh5zq53";
+  release."1.6.1_8.11".version = "1.6.1";
+  release."1.6.0_8.11".sha256 = "0ahxjnzmd7kl3gl38kyjqzkfgllncr2ybnw8bvgrc6iddgga7bpq";
+  release."1.6.0_8.11".version = "1.6.0";
+  release."1.6.0".sha256      = "0kf99i43mlf750fr7fric764mm495a53mg5kahnbp6zcjcxxrm0b";
+  releaseRev = v: "v${v}";
+
+  buildFlags = [ "OCAMLWARN=" ];
+
+  mlPlugin = true;
+  useDuneifVersion = v: lib.versions.isGe "2.2.0" v || v == "dev";
+  propagatedBuildInputs = [ coq.ocamlPackages.findlib elpi ];
+
+  meta = {
+    description = "Coq plugin embedding ELPI";
+    maintainers = [ lib.maintainers.cohencyril ];
+    license = lib.licenses.lgpl21Plus;
+  };
+}).overrideAttrs (o:
+  lib.optionalAttrs (o.version != null
+    && (o.version == "dev" || lib.versions.isGe "2.2.0" o.version))
+  {
+    propagatedBuildInputs = o.propagatedBuildInputs ++ [ coq.ocamlPackages.ppx_optcomp ];
+  })
diff --git a/.nix/ocaml-overlays/elpi/default.nix b/.nix/ocaml-overlays/elpi/default.nix
new file mode 100644
index 000000000..a40d50715
--- /dev/null
+++ b/.nix/ocaml-overlays/elpi/default.nix
@@ -0,0 +1,59 @@
+{ lib
+, buildDunePackage, camlp5
+, ocaml
+, menhir, menhirLib
+, atdgen
+, stdlib-shims
+, re, perl, ncurses
+, ppxlib, ppx_deriving
+, coqPackages
+, version ? "2.0.3"
+}:
+
+let p5 = camlp5; in
+let camlp5 = p5.override { legacy = true; }; in
+
+let fetched = coqPackages.metaFetch ({
+    release."2.0.3".sha256 = "sha256-t2z0sWPiFgp6LuR6CsH/Zk9qfxW+3QjjFcYrB6qSPgc=";
+    release."1.20.0".sha256 = "sha256-lctZAIQgOg5d+LfILtWsBVcsemV3zTZYfJfDlCxHtcA=";
+    release."1.19.2".sha256 = "sha256-dBj5Ek7PWq/8Btq/dggJUqa8cUtfvbi6EWo/lJEDOU4=";
+    release."1.18.1".sha256 = "sha256-rrIv/mVC0Ez3nU7fpnzwduIC3tI6l73DjgAbv1gd2v0=";
+    release."1.17.0".sha256 = "sha256-J8FJBeaB+2HtHjrkgNzOZJngZ2AcYU+npL9Y1HNPnzo=";
+    release."1.15.2".sha256 = "sha256-+sQYQiN3n+dlzXzi5opOjhkJZqpkNwlHZcUjaUM6+xQ=";
+    release."1.15.0".sha256 = "sha256-vpQzbkDqJPCmaBmXcBnzlWGS7djW9wWv8xslkIlXgP0=";
+    releaseRev = v: "v${v}";
+    releaseArtifact = v: if lib.versionAtLeast v "1.13.8"
+      then "elpi-${v}.tbz"
+      else "elpi-v${v}.tbz";
+    location = { domain = "github.com"; owner = "LPCIC"; repo = "elpi"; };
+  }) version;
+in
+buildDunePackage {
+  pname = "elpi";
+  inherit (fetched) version src;
+
+  patches = lib.optional (version == "1.16.5")
+    ./atd_2_10.patch;
+
+  minimalOCamlVersion = "4.07";
+
+  # atdgen is both a library and executable
+  nativeBuildInputs = [ perl ]
+  ++ [ (if lib.versionAtLeast version "1.15" || version == "dev" then menhir else camlp5) ]
+  ++ lib.optional (lib.versionAtLeast version "1.16" || version == "dev") atdgen;
+  buildInputs = [ ncurses ]
+  ++ lib.optional (lib.versionAtLeast version "1.16" || version == "dev") atdgen;
+
+  propagatedBuildInputs = [ re stdlib-shims menhirLib ppxlib ppx_deriving ];
+
+  meta = with lib; {
+    description = "Embeddable λProlog Interpreter";
+    license = licenses.lgpl21Plus;
+    maintainers = [ maintainers.vbgl ];
+    homepage = "https://github.com/LPCIC/elpi";
+  };
+
+  postPatch = ''
+    substituteInPlace elpi_REPL.ml --replace-warn "tput cols" "${ncurses}/bin/tput cols"
+  '';
+}