diff --git a/README.md b/README.md
index ffd871e..0f36383 100644
--- a/README.md
+++ b/README.md
@@ -53,7 +53,7 @@ jobs:
       contents: read
     steps:
       - uses: actions/checkout@v4.2.2
-      - uses: DeterminateSystems/determinate-nix-action@main # or v3.8.4 to pin to a release
+      - uses: DeterminateSystems/determinate-nix-action@main # or v3.8.5 to pin to a release
       - run: nix build .
 ```
 
@@ -67,10 +67,10 @@ jobs:
 Unlike `DeterminateSystems/nix-installer-action`, we fully support explicit version pinning for maximum consistency.
 This Action is **automatically tagged** for every Determinate Nix release, giving you complete control over your CI environment:
 
-📍 Pinning to `DeterminateSystems/determinate-nix-action@v3.8.4` guarantees:
+📍 Pinning to `DeterminateSystems/determinate-nix-action@v3.8.5` guarantees:
 
 - Same `nix-installer-action` revision every time
-- Consistent Determinate Nix v3.8.4 installation
+- Consistent Determinate Nix v3.8.5 installation
 - Reproducible CI workflows, even years later
 
 ✨ Using `@main` instead? You'll:
@@ -112,7 +112,7 @@ updates:
 | `source-branch`         | The branch of `nix-installer` to use (conflicts with `source-tag`, `source-revision`, `source-pr`)                                                                                                                                                                             |          |                            |
 | `source-pr`             | The PR of `nix-installer` to use (conflicts with `source-tag`, `source-revision`, `source-branch`)                                                                                                                                                                             |          |                            |
 | `source-revision`       | The revision of `nix-installer` to use (conflicts with `source-tag`, `source-branch`, `source-pr`)                                                                                                                                                                             |          |                            |
-| `source-tag`            | The tag of `nix-installer` to use (conflicts with `source-revision`, `source-branch`, `source-pr`)                                                                                                                                                                             |          | `v3.8.4`                   |
+| `source-tag`            | The tag of `nix-installer` to use (conflicts with `source-revision`, `source-branch`, `source-pr`)                                                                                                                                                                             |          | `v3.8.5`                   |
 | `source-url`            | A URL pointing to a `nix-installer` executable                                                                                                                                                                                                                                 |          |                            |
 | `backtrace`             | The setting for `RUST_BACKTRACE` (see https://doc.rust-lang.org/std/backtrace/index.html#environment-variables)                                                                                                                                                                |          |                            |
 | `diagnostic-endpoint`   | Diagnostic endpoint url where the installer sends data to. To disable set this to an empty string.                                                                                                                                                                             |          | `-`                        |
diff --git a/action.yml b/action.yml
index 05c52a9..425b88b 100644
--- a/action.yml
+++ b/action.yml
@@ -68,7 +68,7 @@
         "source-tag": {
             "description": "The tag of `nix-installer` to use (conflicts with `source-revision`, `source-branch`, `source-pr`)",
             "required": false,
-            "default": "v3.8.4"
+            "default": "v3.8.5"
         },
         "source-url": {
             "description": "A URL pointing to a `nix-installer` executable",
@@ -101,7 +101,7 @@
         "using": "composite",
         "steps": [
             {
-                "uses": "DeterminateSystems/nix-installer-action@90bb610b90bf290cad97484ba341453bd1cbefea",
+                "uses": "DeterminateSystems/nix-installer-action@428f3c64a3f56011a8bfb3044a519374aff8e7df",
                 "with": {
                     "extra-conf": "${{ inputs.extra-conf }}",
                     "github-server-url": "${{ inputs.github-server-url }}",
diff --git a/flake.lock b/flake.lock
index d958ddc..13ec6a1 100644
--- a/flake.lock
+++ b/flake.lock
@@ -2,12 +2,12 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1753549186,
-        "narHash": "sha256-Znl7rzuxKg/Mdm6AhimcKynM7V3YeNDIcLjBuoBcmNs=",
-        "rev": "17f6bd177404d6d43017595c5264756764444ab8",
-        "revCount": 835620,
+        "lastModified": 1754214453,
+        "narHash": "sha256-Q/I2xJn/j1wpkGhWkQnm20nShYnG7TI99foDBpXm1SY=",
+        "rev": "5b09dc45f24cf32316283e62aec81ffee3c3e376",
+        "revCount": 838708,
         "type": "tarball",
-        "url": "https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.835620%2Brev-17f6bd177404d6d43017595c5264756764444ab8/0198521f-e242-717e-8a25-d1421749c0c3/source.tar.gz"
+        "url": "https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.838708%2Brev-5b09dc45f24cf32316283e62aec81ffee3c3e376/0198762e-0143-77ff-9b8e-5845fdbe02c7/source.tar.gz"
       },
       "original": {
         "type": "tarball",
diff --git a/tools/state.json b/tools/state.json
index 02d0056..ebb8232 100644
--- a/tools/state.json
+++ b/tools/state.json
@@ -1,5 +1,5 @@
 {
-  "nix_installer_action_revision": "90bb610b90bf290cad97484ba341453bd1cbefea",
-  "determinate_nix_tag": "v3.8.4",
+  "nix_installer_action_revision": "428f3c64a3f56011a8bfb3044a519374aff8e7df",
+  "determinate_nix_tag": "v3.8.5",
   "checkout_action_tag": "v4.2.2"
 }