diff --git a/plugins/discourse-details/assets/javascripts/lib/discourse-markdown/details.js b/plugins/discourse-details/assets/javascripts/lib/discourse-markdown/details.js
index 00bd6b670a5..028b9e9bcdf 100644
--- a/plugins/discourse-details/assets/javascripts/lib/discourse-markdown/details.js
+++ b/plugins/discourse-details/assets/javascripts/lib/discourse-markdown/details.js
@@ -2,9 +2,13 @@ const rule = {
   tag: "details",
   before(state, tagInfo) {
     const attrs = tagInfo.attrs;
-    state.push("bbcode_open", "details", 1);
+    const details = state.push("bbcode_open", "details", 1);
     state.push("bbcode_open", "summary", 1);
 
+    if (attrs.open === "") {
+      details.attrs = [["open", ""]];
+    }
+
     let token = state.push("text", "", 0);
     token.content = attrs["_default"] || "";
 
diff --git a/plugins/discourse-details/spec/components/pretty_text_spec.rb b/plugins/discourse-details/spec/components/pretty_text_spec.rb
index cf1e87e6011..28b8b67cc1e 100644
--- a/plugins/discourse-details/spec/components/pretty_text_spec.rb
+++ b/plugins/discourse-details/spec/components/pretty_text_spec.rb
@@ -20,10 +20,25 @@ RSpec.describe PrettyText do
     HTML
   end
 
+  it "supports open attribute" do
+    cooked_html = PrettyText.cook <<~MARKDOWN
+      [details open]
+      bar
+      [/details]
+    MARKDOWN
+
+    expect(cooked_html).to match_html <<~HTML
+      <details open="">
+      <summary></summary>
+        <p>bar</p>
+      </details>
+    HTML
+  end
+
   it "deletes elided content" do
     cooked_html = PrettyText.cook <<~MARKDOWN
       Hello World
-      
+
       <details class='elided'>42</details>
     MARKDOWN