diff --git a/README.txt b/README.txt
index d288f5b..430cf6f 100644
--- a/README.txt
+++ b/README.txt
@@ -13,6 +13,7 @@ FEATURES
   - Theme can be set for single page or list of pages.
   - Theme can be assigned to specific roles.
   - Wildcard '*' character can be used in drupal paths.
+  - Supports query value for theme_key.
   - Supports Multi domain sites.
   - Supports Multilingual sites.
 
diff --git a/src/Form/SwitchPageThemeSettingForm.php b/src/Form/SwitchPageThemeSettingForm.php
index da32015..30492f6 100644
--- a/src/Form/SwitchPageThemeSettingForm.php
+++ b/src/Form/SwitchPageThemeSettingForm.php
@@ -108,13 +108,14 @@ class SwitchPageThemeSettingForm extends ConfigFormBase {
     }
     $form['desc'] = [
       '#type' => 'markup',
-      '#markup' => $this->t('<b>Enabled:</b> Rule will work only if checkbox is checked.<br><b>Pages:</b> Enter one path per line. The "*" character is a wildcard. Example paths are "/node/1" for an individual piece of content or "/node/*" for every piece of content. "@front" is the front page.<br><b>@availableSettings:</b> Select none to allow all.<br><br>Theme with highest weight will be applied on the page.', ['@availableSettings' => $availableSettings, '@front' => '<front>']),
+      '#markup' => $this->t('<b>Enabled:</b> Rule will work only if checkbox is checked.<br><b>Pages:</b> Enter one path per line. The "*" character is a wildcard. Example paths are "/node/1" for an individual piece of content or "/node/*" for every piece of content. "@front" is the front page.<br><b>Theme key:</b> Enter the theme key value to access the selected theme, e.g. ?theme_key=AAABBBCCC<br><b>@availableSettings:</b> Select none to allow all.<br><br>Theme with highest weight will be applied on the page.', ['@availableSettings' => $availableSettings, '@front' => '<front>']),
     ];
 
     // Create headers for table.
     $header = [
       $this->t('Enabled'),
       $this->t('pages'),
+      $this->t('Theme Key'),
       $this->t('Themes'),
       $this->t('Roles'),
     ];
@@ -171,7 +172,7 @@ class SwitchPageThemeSettingForm extends ConfigFormBase {
         '#type' => 'checkbox',
         '#title' => $this->t('Status'),
         '#title_display' => 'invisible',
-        '#default_value' => isset($value['status']) ? $value['status'] : NULL,
+        '#default_value' => isset($value['status']) ? $value['status'] : [],
       ];
 
       $form['spt_table'][$i]['pages'] = [
@@ -184,6 +185,14 @@ class SwitchPageThemeSettingForm extends ConfigFormBase {
         '#default_value' => isset($value['pages']) ? $value['pages'] : [],
       ];
 
+      $form['spt_table'][$i]['theme_key'] = [
+        '#type' => 'textfield',
+        '#title' => $this->t('Theme Key'),
+        '#title_display' => 'invisible',
+        '#size' => 20,
+        '#default_value' => isset($value['theme_key']) ? $value['theme_key'] : [],
+      ];
+
       $form['spt_table'][$i]['theme'] = [
         '#type' => 'select',
         '#title' => $this->t('Theme'),
diff --git a/src/Theme/PageThemeNegotiator.php b/src/Theme/PageThemeNegotiator.php
index 338540a..839183e 100644
--- a/src/Theme/PageThemeNegotiator.php
+++ b/src/Theme/PageThemeNegotiator.php
@@ -128,7 +128,12 @@ class PageThemeNegotiator implements ThemeNegotiatorInterface {
       // Check if rule is enabled.
       if ($value['status'] == 1) {
         // Check condition for basic rules.
-        $condition = ($this->request->getCurrentRequest()->attributes->get("_route") != "system.403" && ($this->pathMatcher->matchPath($this->currentPath->getPath(), $value["pages"]) || $this->pathMatcher->matchPath($this->pathAlias->getAliasByPath($this->currentPath->getPath()), $value["pages"])) && (!array_filter($value["roles"]) || !empty(array_intersect($value["roles"], $this->account->getRoles()))));
+        $condition = (
+          $this->request->getCurrentRequest()->attributes->get("_route") != "system.403" && 
+          ($this->pathMatcher->matchPath($this->currentPath->getPath(), $value["pages"]) || $this->pathMatcher->matchPath($this->pathAlias->getAliasByPath($this->currentPath->getPath()), $value["pages"])) && 
+          (!empty($value["theme_key"]) && $this->request->getCurrentRequest()->get('theme_key') == $value["theme_key"]) &&
+          (!array_filter($value["roles"]) || !empty(array_intersect($value["roles"], $this->account->getRoles())))
+        );
 
         // Check if domain module is enabled.
         if ($this->moduleHandler->moduleExists('domain') && !empty($this->negotiator->getActiveDomain())) {