diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7129b9c895..fa9ece4105 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -137,7 +137,6 @@ jobs:
             let large = ${{ github.repository == 'leanprover/lean4' }};
             let matrix = [
               {
-                // portable release build: use channel with older glibc (2.27)
                 "name": "Linux LLVM",
                 "os": "ubuntu-latest",
                 "release": false,
@@ -152,6 +151,7 @@ jobs:
                 "CMAKE_OPTIONS": "-DLLVM=ON -DLLVM_CONFIG=${GITHUB_WORKSPACE}/build/llvm-host/bin/llvm-config"
               },
               {
+                // portable release build: use channel with older glibc (2.26)
                 "name": "Linux release",
                 "os": large ? "nscloud-ubuntu-22.04-amd64-4x8" : "ubuntu-latest",
                 "release": true,
diff --git a/doc/setup.md b/doc/setup.md
index 28de3664f8..8f66e8765a 100644
--- a/doc/setup.md
+++ b/doc/setup.md
@@ -4,7 +4,7 @@
 
 Platforms built & tested by our CI, available as binary releases via elan (see below)
 
-* x86-64 Linux with glibc 2.27+
+* x86-64 Linux with glibc 2.26+
 * x86-64 macOS 10.15+
 * aarch64 (Apple Silicon) macOS 10.15+
 * x86-64 Windows 11 (any version), Windows 10 (version 1903 or higher), Windows Server 2022
diff --git a/flake.lock b/flake.lock
index 6443026962..76f62f6ec7 100644
--- a/flake.lock
+++ b/flake.lock
@@ -67,12 +67,30 @@
         "type": "github"
       }
     },
+    "nixpkgs-older": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1523316493,
+        "narHash": "sha256-5qJS+i5ECICPAKA6FhPLIWkhPKDnOZsZbh2PHYF1Kbs=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "0b307aa73804bbd7a7172899e59ae0b8c347a62d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "0b307aa73804bbd7a7172899e59ae0b8c347a62d",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs",
         "nixpkgs-cadical": "nixpkgs-cadical",
-        "nixpkgs-old": "nixpkgs-old"
+        "nixpkgs-old": "nixpkgs-old",
+        "nixpkgs-older": "nixpkgs-older"
       }
     },
     "systems": {
diff --git a/flake.nix b/flake.nix
index 372bf8263a..e31257f8c5 100644
--- a/flake.nix
+++ b/flake.nix
@@ -5,17 +5,20 @@
   # old nixpkgs used for portable release with older glibc (2.27)
   inputs.nixpkgs-old.url = "github:NixOS/nixpkgs/nixos-19.03";
   inputs.nixpkgs-old.flake = false;
+  # old nixpkgs used for portable release with older glibc (2.26)
+  inputs.nixpkgs-older.url = "github:NixOS/nixpkgs/0b307aa73804bbd7a7172899e59ae0b8c347a62d";
+  inputs.nixpkgs-older.flake = false;
   # for cadical 1.9.5; sync with CMakeLists.txt
   inputs.nixpkgs-cadical.url = "github:NixOS/nixpkgs/12bf09802d77264e441f48e25459c10c93eada2e";
   inputs.flake-utils.url = "github:numtide/flake-utils";
 
-  outputs = { self, nixpkgs, nixpkgs-old, flake-utils, ... }@inputs: flake-utils.lib.eachDefaultSystem (system:
+  outputs = inputs: inputs.flake-utils.lib.eachDefaultSystem (system:
     let
-      pkgs = import nixpkgs { inherit system; };
+      pkgs = import inputs.nixpkgs { inherit system; };
       # An old nixpkgs for creating releases with an old glibc
-      pkgsDist-old = import nixpkgs-old { inherit system; };
+      pkgsDist-old = import inputs.nixpkgs-older { inherit system; };
       # An old nixpkgs for creating releases with an old glibc
-      pkgsDist-old-aarch = import nixpkgs-old { localSystem.config = "aarch64-unknown-linux-gnu"; };
+      pkgsDist-old-aarch = import inputs.nixpkgs-old { localSystem.config = "aarch64-unknown-linux-gnu"; };
       pkgsCadical = import inputs.nixpkgs-cadical { inherit system; };
       cadical = if pkgs.stdenv.isLinux then
         # use statically-linked cadical on Linux to avoid glibc versioning troubles