diff --git a/app/assets/javascripts/pretty-text/engines/markdown-it/code.js.es6 b/app/assets/javascripts/pretty-text/engines/markdown-it/code.js.es6
index ca54a65ec03..c8d94967a1e 100644
--- a/app/assets/javascripts/pretty-text/engines/markdown-it/code.js.es6
+++ b/app/assets/javascripts/pretty-text/engines/markdown-it/code.js.es6
@@ -21,7 +21,7 @@ function render(tokens, idx, options, env, slf, md) {
     langName = info;
   }
 
-  className = TEXT_CODE_CLASSES.indexOf(langName) !== -1 ? 'lang-nohighlight' : 'lang-' + langName;
+  className = TEXT_CODE_CLASSES.indexOf(info) !== -1 ? 'lang-nohighlight' : 'lang-' + langName;
 
   return `<pre><code class='${className}'>${escapedContent}</code></pre>\n`;
 }
diff --git a/spec/components/pretty_text_spec.rb b/spec/components/pretty_text_spec.rb
index 6cdae573e75..823da26f2e6 100644
--- a/spec/components/pretty_text_spec.rb
+++ b/spec/components/pretty_text_spec.rb
@@ -587,6 +587,8 @@ HTML
 
     it 'can include code class correctly' do
       expect(PrettyText.cook("```cpp\ncpp\n```")).to match_html("<pre><code class='lang-cpp'>cpp\n</code></pre>")
+      expect(PrettyText.cook("```\ncpp\n```")).to match_html("<pre><code class='lang-auto'>cpp\n</code></pre>")
+      expect(PrettyText.cook("```text\ncpp\n```")).to match_html("<pre><code class='lang-nohighlight'>cpp\n</code></pre>")
     end
 
     it 'indents code correctly' do