diff --git a/CHANGELOG.md b/CHANGELOG.md
index c9ede773c..902247ce7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@
     * Updated vendor libraries
     * Use `Symfony EventDispatcher` directly and not rockettheme/toolbox wrapper
 1. [](#bugfix)
+    * Fixed exception caused by missing template type based on `Accept:` header [#2705](https://github.com/getgrav/grav/issues/2705)
     * Fixed `Page::untranslatedLanguages()` not being symmetrical to `Page::translatedLanguages()`
     * Fixed `Flex Pages` not calling `onPageProcessed` event when cached
     * Fixed phpstan issues in Framework up to level 7
diff --git a/composer.json b/composer.json
index e84f36f67..832cf8703 100644
--- a/composer.json
+++ b/composer.json
@@ -45,7 +45,7 @@
         "donatj/phpuseragentparser": "~0.10",
         "pimple/pimple": "~3.2",
         "rockettheme/toolbox": "~1.4",
-        "maximebf/debugbar": "~1.15",
+        "maximebf/debugbar": "~1.0",
         "league/climate": "^3.4",
         "antoligy/dom-string-iterators": "^1.0",
         "miljar/php-exif": "^0.6.4",
diff --git a/system/src/Grav/Common/Twig/Twig.php b/system/src/Grav/Common/Twig/Twig.php
index 63e769061..2984d6652 100644
--- a/system/src/Grav/Common/Twig/Twig.php
+++ b/system/src/Grav/Common/Twig/Twig.php
@@ -290,17 +290,15 @@ class Twig
         $twig_vars['page'] = $item;
         $twig_vars['media'] = $item->media();
         $twig_vars['header'] = $item->header();
-
         $local_twig = clone $this->twig;
 
         $output = '';
+
         try {
             // Process Modular Twig
             if ($item->modularTwig()) {
                 $twig_vars['content'] = $content;
-                $extension = $item->templateFormat();
-                $extension = $extension ? ".{$extension}.twig" : TEMPLATE_EXT;
-                $template = $item->template() . $extension;
+                $template = $this->getPageTwigTemplate($item);
                 $output = $content = $local_twig->render($template, $twig_vars);
             }
 
@@ -310,8 +308,9 @@ class Twig
                 $this->setTemplate($name, $content);
                 $output = $local_twig->render($name, $twig_vars);
             }
+
         } catch (LoaderError $e) {
-            throw new \RuntimeException($e->getRawMessage(), 404, $e);
+            throw new \RuntimeException($e->getRawMessage(), 400, $e);
         }
 
         return $output;
@@ -394,7 +393,6 @@ class Twig
         $twig_vars['header'] = $page->header();
         $twig_vars['media'] = $page->media();
         $twig_vars['content'] = $content;
-        $ext = '.' . ($format ?: 'html') . TWIG_EXT;
 
         // determine if params are set, if so disable twig cache
         $params = $this->grav['uri']->params(null, true);
@@ -403,23 +401,13 @@ class Twig
         }
 
         // Get Twig template layout
-        $template = $this->template($page->template() . $ext);
+        $template = $this->getPageTwigTemplate($page, $format);
 
         try {
             $output = $this->twig->render($template, $vars + $twig_vars);
         } catch (LoaderError $e) {
             $error_msg = $e->getMessage();
-            // Try html version of this template if initial template was NOT html
-            if ($ext !== '.html' . TWIG_EXT) {
-                try {
-                    $page->templateFormat('html');
-                    $output = $this->twig->render($page->template() . '.html' . TWIG_EXT, $vars + $twig_vars);
-                } catch (LoaderError $e) {
-                    throw new \RuntimeException($error_msg, 400, $e);
-                }
-            } else {
-                throw new \RuntimeException($error_msg, 400, $e);
-            }
+            throw new \RuntimeException($error_msg, 400, $e);
         }
 
         return $output;
@@ -460,6 +448,22 @@ class Twig
         return $this->template ?? $template;
     }
 
+    public function getPageTwigTemplate($page, $format = null)
+    {
+        $template = $page->template();
+        $extension = $format ?: $page->templateFormat();
+        $twig_extension = $extension ? '.'. $extension .TWIG_EXT : TEMPLATE_EXT;
+        $template_file = $this->template($page->template() . $twig_extension);
+
+        if ($this->twig->getLoader()->exists($template_file)) {
+            return $template_file;
+        } else {
+            // Default to HTML
+            $page->templateFormat('html');
+            return $template . TEMPLATE_EXT;
+        }
+    }
+
     /**
      * Overrides the autoescape setting
      *