diff --git a/src/Infrastructure/File/ArchiveHandler.php b/src/Infrastructure/File/ArchiveHandler.php
index b7388c0a9..85b1fe671 100644
--- a/src/Infrastructure/File/ArchiveHandler.php
+++ b/src/Infrastructure/File/ArchiveHandler.php
@@ -73,7 +73,16 @@ public function compressDirectory(string $directory, ?string $regex = null): str
         $umask = umask(self::OWNER_ONLY);
 
         try {
-            $this->archive->buildFromDirectory($directory, $regex);
+            // Only pass the pattern when there is one. `?string $regex = null` offers "archive
+            // the whole directory" as an option, and `PharData::buildFromDirectory()` declares its
+            // second parameter `string` — so taking that option emits a deprecation on PHP 8.5,
+            // becomes a fatal on PHP 9, and is already a hard error under the test suite's error
+            // handler. The one-argument form is what "no pattern" means to Phar.
+            if ($regex === null) {
+                $this->archive->buildFromDirectory($directory);
+            } else {
+                $this->archive->buildFromDirectory($directory, $regex);
+            }
 
             // Before compressing, not only after: the uncompressed archive holds the same thing
             // the compressed one does and exists for as long as compressing takes, which on a
diff --git a/tests/Unit/Infrastructure/File/ArchiveHandlerTest.php b/tests/Unit/Infrastructure/File/ArchiveHandlerTest.php
index 6b161749f..9e294e51e 100644
--- a/tests/Unit/Infrastructure/File/ArchiveHandlerTest.php
+++ b/tests/Unit/Infrastructure/File/ArchiveHandlerTest.php
@@ -50,10 +50,8 @@
 class ArchiveHandlerTest extends TestCase
 {
     /**
-     * The one production caller always passes a regex (`BackupFile::BACKUP_INCLUDE_REGEX`), and so
-     * does this — `compressDirectory()`'s `?string $regex = null` default reaches
-     * `PharData::buildFromDirectory()`, which requires a string, so the null is a TypeError. It is
-     * unreachable today and is not this change's to fix.
+     * The one production caller passes a regex (`BackupFile::BACKUP_INCLUDE_REGEX`); most of these
+     * do too, and one below takes the other option deliberately.
      */
     private const EVERYTHING = '/.*/';
 
@@ -132,6 +130,29 @@ public function theCompressedArchiveIsOwnerOnly(): void
         self::assertSame(0600, fileperms($this->archivePath()) & 0777);
     }
 
+    /**
+     * Archiving a whole directory, which is what `?string $regex = null` offers.
+     *
+     * Taking that option handed the null straight to `PharData::buildFromDirectory()`, whose second
+     * parameter is declared `string` — a deprecation on PHP 8.5, a fatal on PHP 9, and already a
+     * hard error under this suite's error handler, which is how it was found. The one production
+     * caller always passes a regex, so nothing had reached it.
+     *
+     * Asserted on the contents rather than on the absence of an error: the fix is the one-argument
+     * form, and the thing worth pinning is that it still archives everything.
+     */
+    #[Test]
+    public function aDirectoryCanBeArchivedWithNoPatternAtAll(): void
+    {
+        file_put_contents($this->source . DIRECTORY_SEPARATOR . 'second.txt', 'more');
+
+        $this->handler()->compressDirectory($this->source);
+
+        $entries = iterator_to_array(new PharData($this->archivePath()));
+
+        self::assertCount(2, $entries);
+    }
+
     /**
      * And nothing is left beside it — the uncompressed tar, which holds exactly the same thing,
      * is removed once the gz exists.