diff --git a/blocks/moodleblock.class.php b/blocks/moodleblock.class.php
index 9c58f63d3d4..c912d51ae23 100644
--- a/blocks/moodleblock.class.php
+++ b/blocks/moodleblock.class.php
@@ -429,13 +429,13 @@ class block_base {
     function html_attributes() {
         $attributes = array(
             'id' => 'inst' . $this->instance->id,
-            'class' => 'block_' . $this->name(). '  block',
+            'class' => 'block_' . $this->name() . ' block',
             'role' => $this->get_aria_role()
         );
         if ($this->hide_header()) {
             $attributes['class'] .= ' no-header';
         }
-        if ($this->instance_can_be_docked() && get_user_preferences('docked_block_instance_'.$this->instance->id, 0)) {
+        if ($this->instance_can_be_docked() && get_user_preferences('docked_block_instance_' . $this->instance->id, 0)) {
             $attributes['class'] .= ' dock_on_load';
         }
         return $attributes;
diff --git a/lib/outputrenderers.php b/lib/outputrenderers.php
index 1c1e45e5266..3901907b466 100644
--- a/lib/outputrenderers.php
+++ b/lib/outputrenderers.php
@@ -1747,6 +1747,7 @@ class core_renderer extends renderer_base {
         $context->showskiplink = !empty($context->skiptitle);
         $context->arialabel = $bc->arialabel;
         $context->ariarole = !empty($bc->attributes['role']) ? $bc->attributes['role'] : 'complementary';
+        $context->class = $bc->attributes['class'];
         $context->type = $bc->attributes['data-block'];
         $context->title = $bc->title;
         $context->content = $bc->content;
diff --git a/lib/templates/block.mustache b/lib/templates/block.mustache
index 09560bc8915..a08aeed7166 100644
--- a/lib/templates/block.mustache
+++ b/lib/templates/block.mustache
@@ -4,6 +4,7 @@
     Example context (json):
     {
         "id": "block0",
+        "class": "block block_html",
         "showskiplink": true,
         "type": "html",
         "ariarole": "complementary",
@@ -20,7 +21,7 @@
 
 {{! Start Block Container }}
 <section id="{{id}}"
-     class="{{#hidden}}hidden{{/hidden}} block block_{{type}} {{#hascontrols}}block_with_controls{{/hascontrols}} card mb-3"
+     class="{{#hidden}}hidden{{/hidden}} {{class}} {{#hascontrols}}block_with_controls{{/hascontrols}} card mb-3"
      role="{{ariarole}}"
      data-block="{{type}}"
      {{#arialabel}}