diff --git a/nix/api-doc.nix b/nix/api-doc.nix
index bb0f15e3a523413180104c772f7ba86b831ce2d1..b0c7d93aea9fbc7ed37abb23790215154c267e5f 100644
--- a/nix/api-doc.nix
+++ b/nix/api-doc.nix
@@ -22,7 +22,7 @@ stdenv.mkDerivation rec {
     dune build -j1 --error-reporting=twice @doc
     cp -r _build/default/_doc/_html frama-c-api
     echo ".dummy" > excluded
-    tar czf frama-c-api.tar.gz -X excluded frama-c-api
+    tar czf frama-c-api.tar.gz -X excluded --owner=0 --group=0 --numeric-owner --sort=name --mtime="$(date --iso-8601 --date "today 00:00:00") 00:00Z" frama-c-api
 
     make server-doc NO_BUILD_FRAMAC=yes
     cp -r doc/server frama-c-server-api
diff --git a/nix/api-json-doc.nix b/nix/api-json-doc.nix
index 47ae4d36acefe26d700a584290e476409d57a568..35125f4131e8f893539a93a0389275f66d50a64e 100644
--- a/nix/api-json-doc.nix
+++ b/nix/api-json-doc.nix
@@ -22,7 +22,7 @@ stdenv.mkDerivation rec {
     dune build -j1 --error-reporting=twice @doc-json
     cp -r _build/default/_doc/_html frama-c-api-json
     echo ".dummy" > excluded
-    tar czf frama-c-api-json.tar.gz -X excluded frama-c-api-json
+    tar czf frama-c-api-json.tar.gz -X excluded --owner=0 --group=0 --numeric-owner --sort=name --mtime="$(date --iso-8601 --date "today 00:00:00") 00:00Z" frama-c-api-json
   '';
 
   installPhase = ''