diff --git a/Sources/Avatar.php b/Sources/Avatar.php
index 7df9e0605e..60c1d10607 100644
--- a/Sources/Avatar.php
+++ b/Sources/Avatar.php
@@ -501,14 +501,14 @@ public function __construct(
 
 					break;
 
-				// Is the file in the prepackaged avatar directory?
+				// Is the file in the avatar gallery directory?
 				case 2:
 					if (
 						!empty($this->filename)
 						&& !empty(Config::$modSettings['avatar_url'])
-						&& is_file(Config::$boarddir . '/avatars/' . ltrim($this->filename, '\\/'))
+						&& is_file(self::getGalleryDir() . '/' . ltrim($this->filename, '\\/'))
 						&& Utils::checkMimeType(
-							Config::$boarddir . '/avatars/' . ltrim($this->filename, '\\/'),
+							self::getGalleryDir() . '/' . ltrim($this->filename, '\\/'),
 							'image/',
 							true,
 						)
@@ -558,7 +558,7 @@ public function __construct(
 							fn($path) => Sapi::canonicalPath($path) . DIRECTORY_SEPARATOR,
 							array_filter([
 								Config::$modSettings['custom_avatar_dir'] ?? '',
-								Config::$boarddir . '/avatars',
+								self::getGalleryDir(),
 							]),
 						);
 
@@ -579,7 +579,7 @@ public function __construct(
 				case 5:
 					if (
 						!empty(Config::$modSettings['avatar_url'])
-						&& is_file(Config::$boarddir . '/avatars/default.png')
+						&& is_file(self::getGalleryDir() . '/default.png')
 					) {
 						$url = new Url(Config::$modSettings['avatar_url'] . '/default.png');
 					}
@@ -804,4 +804,26 @@ private function getExternal(): string
 			default => 'http://',
 		};
 	}
+
+	/*************************
+	 * Internal static methods
+	 *************************/
+
+	/**
+	 * The directory that holds the gallery of avatars members can choose from.
+	 *
+	 * This is the directory the admin nominated, which is the one the gallery
+	 * is listed from and the one a chosen avatar is checked against before it
+	 * is saved. Config::$modSettings['avatar_url'] is the address of the same
+	 * directory, so the two have to name the same place or a member's choice
+	 * resolves to an address with nothing behind it.
+	 *
+	 * @return string Path to the avatar gallery directory.
+	 */
+	private static function getGalleryDir(): string
+	{
+		return !empty(Config::$modSettings['avatar_directory'])
+			? Config::$modSettings['avatar_directory']
+			: Config::$boarddir . '/avatars';
+	}
 }
diff --git a/tests/Unit/AvatarGalleryDirectoryTest.php b/tests/Unit/AvatarGalleryDirectoryTest.php
new file mode 100644
index 0000000000..0f2d524c97
--- /dev/null
+++ b/tests/Unit/AvatarGalleryDirectoryTest.php
@@ -0,0 +1,130 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SMF\Tests\Unit;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use SMF\Avatar;
+use SMF\Config;
+
+/**
+ * Covers which directory SMF\Avatar looks in for a gallery avatar.
+ *
+ * The gallery lives wherever Config::$modSettings['avatar_directory'] says it
+ * does. Themes/default/images stands in for an admin who moved it: it is full
+ * of images, it is not the directory SMF ships the gallery in, and nothing has
+ * to be written to disk to use it.
+ */
+#[CoversClass(Avatar::class)]
+class AvatarGalleryDirectoryTest extends TestCase
+{
+	/*********************
+	 * Internal properties
+	 *********************/
+
+	/**
+	 * @var array The settings this class reads, as they were before the test.
+	 */
+	private array $backup = [];
+
+	/**
+	 * @var string Config::$boardurl as it was before the test.
+	 */
+	private string $boardurl = '';
+
+	/****************
+	 * Public methods
+	 ****************/
+
+	/**
+	 * The admin can move the avatar gallery, and the admin panel offers the
+	 * setting and warns when the directory it names is not there. Profile
+	 * lists the gallery out of that directory and refuses to save a choice
+	 * from anywhere else, so it is the directory a stored avatar is a path
+	 * into, and it is where the file has to be looked for.
+	 */
+	public function testAGalleryAvatarIsLookedForInTheConfiguredDirectory(): void
+	{
+		$this->setUpForum(Config::$boarddir . '/Themes/default/images');
+
+		$avatar = new Avatar(url: 'cake.png', id_member: 1);
+
+		$this->assertSame('https://example.com/gallery/cake.png', (string) $avatar->url);
+	}
+
+	public function testTheSameForAFileInASubdirectoryOfTheGallery(): void
+	{
+		$this->setUpForum(Config::$boarddir . '/Themes/default/images');
+
+		$avatar = new Avatar(url: 'icons/bell.png', id_member: 1);
+
+		$this->assertSame('https://example.com/gallery/icons/bell.png', (string) $avatar->url);
+	}
+
+	/**
+	 * A forum whose admin never touched the setting keeps the gallery SMF
+	 * ships, so the value the installer would have written is the fallback.
+	 */
+	public function testTheShippedGalleryIsUsedWhenNothingSaysOtherwise(): void
+	{
+		$this->setUpForum(null);
+
+		$avatar = new Avatar(url: 'Oxygen/beagle.png', id_member: 1);
+
+		$this->assertSame('https://example.com/gallery/Oxygen/beagle.png', (string) $avatar->url);
+	}
+
+	/******************
+	 * Internal methods
+	 ******************/
+
+	protected function setUp(): void
+	{
+		$this->boardurl = Config::$boardurl ?? '';
+
+		foreach (['avatar_url', 'avatar_directory', 'gravatarEnabled'] as $key) {
+			if (isset(Config::$modSettings[$key])) {
+				$this->backup[$key] = Config::$modSettings[$key];
+			}
+		}
+	}
+
+	/**
+	 * PHPUnit does not reset SMF's statics between tests, so a setting left
+	 * behind here would leak into every test that follows.
+	 */
+	protected function tearDown(): void
+	{
+		Config::$boardurl = $this->boardurl;
+
+		foreach (['avatar_url', 'avatar_directory', 'gravatarEnabled'] as $key) {
+			unset(Config::$modSettings[$key]);
+
+			if (isset($this->backup[$key])) {
+				Config::$modSettings[$key] = $this->backup[$key];
+			}
+		}
+
+		$this->backup = [];
+	}
+
+	/**
+	 * Puts the gallery in $directory, or leaves the setting off entirely when
+	 * it is null. The URL is deliberately not the shipped one, so that an
+	 * address built from it cannot be mistaken for a lucky guess.
+	 */
+	private function setUpForum(?string $directory): void
+	{
+		Config::$boardurl = 'https://example.com';
+		Config::$modSettings['avatar_url'] = 'https://example.com/gallery';
+		Config::$modSettings['gravatarEnabled'] = false;
+
+		if ($directory === null) {
+			unset(Config::$modSettings['avatar_directory']);
+		} else {
+			Config::$modSettings['avatar_directory'] = $directory;
+		}
+	}
+}