diff --git a/box.json b/box.json
index 6d59f39d..624ee131 100644
--- a/box.json
+++ b/box.json
@@ -27,13 +27,13 @@
       "name": [
         "*.php",
         "*.xml",
-        "*.sh"
+        "*.sh",
+        "*.jar"
       ],
       "exclude": [
         "Tests",
         "tests",
         "Docs",
-        "node_modules",
         "pix"
       ]
     }
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 91d43b25..8b62d0f4 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -9,6 +9,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 The format of this change log follows the advice given at [Keep a CHANGELOG](http://keepachangelog.com).
 
 ## [Unreleased]
+### Fixed
+- Fix the `mustache` command to work from within the PHAR archive.
+
 ## [4.1.3] - 2023-09-08
 ### Changed
 - Updated project dependencies to current [moodle-cs](https://github.com/moodlehq/moodle-cs), [moodle-local_moodlecheck](https://github.com/moodlehq/moodle-local_moodlecheck) and [moodle-local_ci](https://github.com/moodlehq/moodle-local_ci) versions. Also, to various internal / development tools.
diff --git a/src/Command/MustacheCommand.php b/src/Command/MustacheCommand.php
index d671f577..45cb29f7 100644
--- a/src/Command/MustacheCommand.php
+++ b/src/Command/MustacheCommand.php
@@ -52,9 +52,13 @@ protected function execute(InputInterface $input, OutputInterface $output): int
         $jarFile = $this->resolveJarFile();
 
         // This is a workaround to execute mustache_lint.php file from within a phar.
+        // (by copying both the script and the jar file to a temporary directory)
         $filesystem = new Filesystem();
-        $wrapper    = tempnam(sys_get_temp_dir(), 'mustache-linter-wrapper');
+        $tmpDir     = sys_get_temp_dir();
+        $wrapper    = tempnam($tmpDir, 'mustache-linter-wrapper');
+        $jarTmpFile = $tmpDir . '/vnu.jar';
         $filesystem->dumpFile($wrapper, sprintf('<?php include \'%s\';', $linter));
+        $filesystem->copy($jarFile, $jarTmpFile, true);
 
         $code = 0;
         foreach ($files as $file) {
@@ -68,7 +72,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
                 'php',
                 $wrapper,
                 '--filename=' . $file,
-                '--validator=' . $jarFile,
+                '--validator=' . $jarTmpFile,
                 '--basename=' . $this->moodle->directory,
             ];
             // _JAVA_OPTIONS is something Travis CI started to set in Trusty.  This breaks Mustache because
@@ -82,6 +86,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
         }
 
         $filesystem->remove($wrapper);
+        $filesystem->remove($jarTmpFile);
 
         return $code;
     }
@@ -94,6 +99,11 @@ private function resolveJarFile(): string
         // Check if locally installed.
         $file = __DIR__ . '/../../vendor/moodlehq/moodle-local_ci/node_modules/vnu-jar/build/dist/vnu.jar';
         if (is_file($file)) {
+            if (\Phar::running() !== '') {
+                // No need to use realpath() when running from a phar.
+                return $file;
+            }
+
             return realpath($file);
         }