diff --git a/Sources/Profile.php b/Sources/Profile.php
index 395a97ff9c..0f42735b0a 100644
--- a/Sources/Profile.php
+++ b/Sources/Profile.php
@@ -1140,28 +1140,37 @@ public function loadCustomFields(string $area = 'summary'): void
 	}
 
 	/**
-	 * Loads the theme options for the member.
+	 * Populates Utils::$context['member']['options'] with this member's theme
+	 * options.
 	 *
-	 * @param bool $defaultSettings If true, we are loading default options.
+	 * @param ?bool $default_only If true, only load options for the default
+	 *    theme, where "default theme" means whichever theme is used for guests.
+	 *    Default: false.
 	 */
-	public function loadThemeOptions(bool $defaultSettings = false)
+	public function loadThemeOptions(bool $default_only = false)
 	{
-		if (isset($_POST['default_options'])) {
-			$_POST['options'] = isset($_POST['options']) ? $_POST['options'] + $_POST['default_options'] : $_POST['default_options'];
+		// Get this member's current theme options.
+		if ($default_only && $this->theme != (Config::$modSettings['theme_guests'] ?? 1)) {
+			$temp = $this->data['options'] ?? [];
+			parent::loadOptions($this->id, $default_only);
+			Utils::$context['member']['options'] = $this->data['options'];
+			$this->data['options'] = $temp;
+		} else {
+			Utils::$context['member']['options'] = $this->data['options'] ?? [];
 		}
 
-		Utils::$context['member']['options'] = $this->data['options'] ?? [];
+		// Overwrite their current options with anything that is being set to a
+		// new value.
+		$_POST['options'] = ($_POST['options'] ?? []) + ($_POST['default_options'] ?? []);
 
-		if (isset($_POST['options']) && \is_array($_POST['options'])) {
-			foreach ($_POST['options'] as $k => $v) {
-				Utils::$context['member']['options'][$k] = $v;
-			}
+		foreach ($_POST['options'] as $k => $v) {
+			Utils::$context['member']['options'][$k] = $v;
 		}
 
-		// Load up the default theme options for any missing.
-		parent::loadOptions(-1);
+		// If any theme options are still missing, set them to default values.
+		parent::loadOptions(-1, $default_only);
 
-		foreach (parent::$profiles[-1]['options'] as $k => $v) {
+		foreach (parent::$profiles[-1]['options'] ?? [] as $k => $v) {
 			if (!isset(Utils::$context['member']['options'][$k])) {
 				Utils::$context['member']['options'][$k] = $v;
 			}
diff --git a/Sources/User.php b/Sources/User.php
index 05022b005b..e677bfd0e0 100644
--- a/Sources/User.php
+++ b/Sources/User.php
@@ -4774,23 +4774,52 @@ protected static function loadUserData(array $users, int $type = self::LOAD_BY_I
 	 * Loads theme options for the given users.
 	 *
 	 * @param array|int $ids One or more user ID numbers.
+	 * @param ?bool $default_only If true, only load options for the default
+	 *    theme, where "default theme" means whichever theme is used for guests.
+	 *    Default: false.
 	 */
-	protected static function loadOptions(array|int $ids): void
+	protected static function loadOptions(array|int $ids, bool $default_only = false): void
 	{
 		$ids = (array) $ids;
 
 		$request = Db::$db->query(
 			'SELECT id_member, id_theme, variable, value
 			FROM {db_prefix}themes
-			WHERE id_member IN ({array_int:ids})',
+			WHERE id_member IN ({array_int:ids})
+			ORDER BY id_theme',
 			[
 				'ids' => $ids,
 			],
 		);
 
 		while ($row = Db::$db->fetch_assoc($request)) {
-			self::$profiles[$row['id_member']]['options'][$row['variable']] = $row['value'];
+			// Which theme is used for guests?
+			$guest_theme = (int) (Config::$modSettings['theme_guests'] ?? 1);
+
+			// Which theme is this member using?
+			$user_theme = $default_only ? $guest_theme : (int) (self::$profiles[$row['id_member']]['id_theme'] ?? $guest_theme);
+
+			if (
+				// Rows are returned in ascending order by id_theme, so we start
+				// with theme 1's value and then overwrite as needed.
+				$row['id_theme'] == 1
+				// If the guest theme isn't theme 1, then overwrite the value
+				// from theme 1 with the value from the guest theme.
+				|| (
+					$row['id_theme'] == $guest_theme
+					// Special check needed here to ensure the guest theme does
+					// not overwrite the user's preferred theme. For example, if
+					// the guest theme is 5 but the user's theme is 2, then we
+					// want to keep the value from theme 2.
+					&& $guest_theme < $user_theme
+				)
+				// The value from the user's preferred theme takes precedence.
+				|| $row['id_theme'] == $user_theme
+			) {
+				self::$profiles[$row['id_member']]['options'][$row['variable']] = $row['value'];
+			}
 		}
+
 		Db::$db->free_result($request);
 	}