diff --git a/.castor/docker.php b/.castor/docker.php
index 47c5d1c..9ab26fb 100644
--- a/.castor/docker.php
+++ b/.castor/docker.php
@@ -102,6 +102,7 @@ function build(
     ?string $profile = null,
 ): void {
     generate_certificates(force: false);
+    normalize_build_contexts_permissions();
 
     io()->title('Building infrastructure');
 
@@ -590,6 +591,10 @@ function push(
 
     $services = get_services();
 
+    if (!$dryRun) {
+        normalize_build_contexts_permissions($services);
+    }
+
     // Only services with a cache_from can push their build cache back to the registry.
     $cacheFroms = array_filter(array_map(
         static fn (array $config) => $config['build']['cache_from'][0] ?? null,
@@ -641,6 +646,75 @@ function push(
     run([...$command, ...array_keys($cacheFroms)], context: $c);
 }
 
+/**
+ * The build cache depends on the permissions of the files of the build context: a
+ * checkout made with a 002 umask (664 files) never reuses the cache pushed by the CI
+ * (644 files). Gives the files tracked by git their git permissions (644 or 755, and
+ * 755 for their directories), whatever the umask.
+ *
+ * Untracked files (certificates...) and additional build contexts (e.g. the
+ * application of the production images) are left untouched.
+ *
+ * @param array<string, array{build?: array{context?: string}}>|null $services
+ */
+function normalize_build_contexts_permissions(?array $services = null): void
+{
+    if (variable('power_shell')) {
+        return;
+    }
+
+    $rootDir = variable('root_dir');
+
+    $contexts = [];
+    foreach ($services ?? get_services() as $service) {
+        $buildContext = $service['build']['context'] ?? null;
+
+        // Only local directories of the project (not a git URL, for instance)
+        if ($buildContext && str_starts_with($buildContext, $rootDir . '/') && is_dir($buildContext)) {
+            $contexts[$buildContext] = true;
+        }
+    }
+
+    if (!$contexts) {
+        return;
+    }
+
+    $process = run(
+        ['git', 'ls-files', '--stage', '-z', '--', ...array_keys($contexts)],
+        context: context()->withQuiet()->withAllowFailure()->withWorkingDirectory($rootDir),
+    );
+
+    // Not a git repository
+    if (!$process->isSuccessful()) {
+        return;
+    }
+
+    $directories = [];
+    foreach (explode("\0", trim($process->getOutput(), "\0")) as $entry) {
+        // "<mode> <object> <stage>\t<file>"
+        [$metadata, $file] = explode("\t", $entry, 2) + [1 => ''];
+        $mode = substr($metadata, 0, 6);
+        $path = "{$rootDir}/{$file}";
+
+        // Symbolic links and submodules have no permissions of their own
+        if (!\in_array($mode, ['100644', '100755'], true) || !is_file($path)) {
+            continue;
+        }
+
+        chmod($path, '100755' === $mode ? 0o755 : 0o644);
+
+        foreach (array_keys($contexts) as $buildContext) {
+            for ($directory = \dirname($path); str_starts_with($directory . '/', $buildContext . '/'); $directory = \dirname($directory)) {
+                $directories[$directory] = true;
+            }
+        }
+    }
+
+    foreach (array_keys($directories) as $directory) {
+        chmod($directory, 0o755);
+    }
+}
+
 /**
  * @return array<string, array{image?: string, profiles?: list<string>, build: array{context: string, dockerfile?: string, cache_from?: list<string>, target?: string, additional_contexts?: array<string, string>}}>
  */
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8563174..3bb0867 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,6 +29,7 @@
   * Mount the project in `/var/www` instead of `/home/app`
   * Add git worktree support (auto-isolated project name, ports, volumes, networks)
   * Add support for caching image cache in a registry
+  * Give the build contexts files their git permissions before building, so the registry cache is reused whatever the umask
   * Also use the GitHub Actions cache (`type=gha`) in the CI, through `docker-compose.ci.yml`
   * Add production images (`php` and `nginx`): code baked in, non-root, php-fpm on a unix socket
   * Share php-fpm and nginx configuration between the dev `frontend` container and the production images
diff --git a/README.md b/README.md
index 2ac2068..03b55d3 100644
--- a/README.md
+++ b/README.md
@@ -1174,6 +1174,12 @@ castor docker:push
 > depending on your environment. It is recommended to push the cache from the CI
 > environment.
 
+> [!NOTE]
+> The build cache depends on the permissions of the files of the build context.
+> With a `002` umask, a checkout gets `664` files instead of the `644` ones of
+> the CI, and would never reuse its cache: `castor docker:build` and `castor
+> docker:push` give the files tracked by git their git permissions first.
+
 This command will generate a bake file with the images to push from the
 `cache_from` directive of the `docker-compose.yml` file. If you want to add more
 images to push, you can add the `cache_from` directive to them.