diff --git a/nix/default.nix b/nix/default.nix
index 985c13130cb2263a113625feb1286134e033b715..00ff4cb5399776d1ec0de09935e05d5c4d620a15 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -63,7 +63,8 @@ rec {
   lint = stdenv.mkDerivation {
         name = "frama-c-lint";
         inherit src;
-        buildInputs = (mk_buildInputs {opamPackages = [ "ocp-indent" ];} ) ++ [ pkgs.bc plugins.headache.installed ];
+        buildInputs = (mk_buildInputs { opamPackages = [ { name = "ocp-indent"; constraint = "=1.6.1"; } ];} )
+                      ++ [ pkgs.bc plugins.headache.installed ];
         outputs = [ "out" ];
         postPatch = ''
                patchShebangs .
@@ -228,7 +229,7 @@ rec {
                 sed -i src/plugins/pathcrawler/extern/eclipseCLP/RUNME -e "s/chmod 2755/chmod 755/g"
                 rm src/plugins/pathcrawler/extern/eclipseCLP/lib/x86_64_linux/dbi_mysql.so
                 rm src/plugins/pathcrawler/extern/eclipseCLP/lib/x86_64_linux/ic.so
-                prefix="src/plugins/pathcrawler" autoPatchelf
+                autoPatchelf src/plugins/pathcrawler
                 make -j 4
                 ln -sr src/plugins/pathcrawler/share share/pc
                 make tests -j4 PTESTS_OPTS="-error-code -j 4"
diff --git a/nix/frama-ci.nix b/nix/frama-ci.nix
index 3976ce7088a3c25cb19a0f142a0452a3526cb14a..fb32fb772345f36d509b68e0ef3ea04213545105 100644
--- a/nix/frama-ci.nix
+++ b/nix/frama-ci.nix
@@ -5,8 +5,8 @@ let
     src = builtins.fetchGit {
             "url" = "https://bobot:${password}@git.frama-c.com/frama-c/Frama-CI.git";
             "name" = "Frama-CI";
-            "rev" = "ed541f6e3818da2bf31125740b8555acb086ca29";
-            "ref" = "feature/andre/yojson-mandatory-dependence";
+            "rev" = "cea0f2d2872e59fd3e6fe4634891a3765c7036e8";
+            "ref" = "feature/opam2";
     };
  in
  {
diff --git a/nix/frama-ci.sh b/nix/frama-ci.sh
index b4a69f90154968218273a70d50be6173a2909841..b331b057a8e8ec372a541e94d2af935a95b94f2a 100755
--- a/nix/frama-ci.sh
+++ b/nix/frama-ci.sh
@@ -4,7 +4,7 @@ DIR=$(dirname $0)
 
 export FRAMA_CI_NIX=$DIR/frama-ci.nix
 
-export FRAMA_CI=$(nix-instantiate --eval -E "((import <nixpkgs> {}).callPackage $FRAMA_CI_NIX  { password = \"$TOKEN_FOR_API\";}).src.outPath")
+export FRAMA_CI=$(nix-instantiate --eval -E "((import <nixos-19.03> {}).callPackage $FRAMA_CI_NIX  { password = \"$TOKEN_FOR_API\";}).src.outPath")
 
 FRAMA_CI=${FRAMA_CI#\"}
 FRAMA_CI=${FRAMA_CI%\"}