diff --git a/src/nix/NOTES.md b/src/nix/NOTES.md
index b3b53476a..05fe329e1 100644
--- a/src/nix/NOTES.md
+++ b/src/nix/NOTES.md
@@ -2,6 +2,10 @@
 
 This Feature should work on recent versions of Debian/Ubuntu, RedHat Enterprise Linux, Fedora, RockyLinux, and Alpine Linux.
 
+## Nix store persistence
+
+On 1.3.x, option changes may not be reflected after a rebuild, because `/nix` is mounted from a Docker volume that keeps the store built the first time. Either install packages from `postCreateCommand` with `nix-env` so they land in that volume, or upgrade to 1.4.0 or later, which drops the mount.
+
 ## Location of Flakes
 
 Currently `flakeUri` works best with a remote URI (e.g., `github:nixos/nixpkgs/nixpkgs-unstable#hello`) as local files need to be in the image.
diff --git a/src/nix/README.md b/src/nix/README.md
index 4fd9700f3..ea97ad65b 100644
--- a/src/nix/README.md
+++ b/src/nix/README.md
@@ -26,6 +26,10 @@ Installs the Nix package manager and optionally a set of packages.
 
 This Feature should work on recent versions of Debian/Ubuntu, RedHat Enterprise Linux, Fedora, RockyLinux, and Alpine Linux.
 
+## Nix store persistence
+
+On 1.3.x, option changes may not be reflected after a rebuild, because `/nix` is mounted from a Docker volume that keeps the store built the first time. Either install packages from `postCreateCommand` with `nix-env` so they land in that volume, or upgrade to 1.4.0 or later, which drops the mount.
+
 ## Location of Flakes
 
 Currently `flakeUri` works best with a remote URI (e.g., `github:nixos/nixpkgs/nixpkgs-unstable#hello`) as local files need to be in the image.
diff --git a/src/nix/devcontainer-feature.json b/src/nix/devcontainer-feature.json
index 63723e591..f2e956d8a 100644
--- a/src/nix/devcontainer-feature.json
+++ b/src/nix/devcontainer-feature.json
@@ -1,6 +1,6 @@
 {
     "id": "nix",
-    "version": "1.3.1",
+    "version": "1.4.0",
     "name": "Nix Package Manager",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/nix",
     "description": "Installs the Nix package manager and optionally a set of packages.",
@@ -57,12 +57,5 @@
     "containerEnv": {
         "PATH": "/nix/var/nix/profiles/default/bin:/nix/var/nix/profiles/default/sbin:${PATH}"
     },
-    "mounts": [
-        {
-            "source": "nix-store-${devcontainerId}",
-            "target": "/nix",
-            "type": "volume"
-        }
-    ],
     "entrypoint": "/usr/local/share/nix-entrypoint.sh"
 }
diff --git a/test/nix/extra-config-packages.sh b/test/nix/extra-config-packages.sh
new file mode 100755
index 000000000..25312c04c
--- /dev/null
+++ b/test/nix/extra-config-packages.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+set -e
+
+source dev-container-features-test-lib
+
+check "Nix installation is not masked by a volume" bash -c "! mountpoint -q /nix"
+check "Experimental features config" grep -E '^experimental-features = nix-command flakes$' /etc/nix/nix.conf
+check "hello_installed" type hello
+check "hello_in_default_profile" bash -lc "nix-env -p /nix/var/nix/profiles/default -q | grep -q '^hello'"
+
+reportResults
\ No newline at end of file
diff --git a/test/nix/scenarios.json b/test/nix/scenarios.json
index 3fb839629..47340c073 100644
--- a/test/nix/scenarios.json
+++ b/test/nix/scenarios.json
@@ -108,5 +108,15 @@
                 "extraNixConfig": "extra-substituters = https://foo.cachix.org,extra-trusted-public-keys = foo.cachix.org-1:bar="
             }
         }
+    },
+    "extra-config-packages": {
+        "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
+        "remoteUser": "vscode",
+        "features": {
+            "nix": {
+                "extraNixConfig": "experimental-features = nix-command flakes",
+                "packages": "hello"
+            }
+        }
     }
 }