diff --git a/tools/doc/html.js b/tools/doc/html.js
index 243fbfea9de692..4613ab7ec5c59d 100644
--- a/tools/doc/html.js
+++ b/tools/doc/html.js
@@ -189,13 +189,10 @@ function preprocessElements({ filename }) {
             `No language set in ${filename}, ` +
             `line ${node.position.start.line}`);
         }
-        const language = (node.lang || '').split(' ')[0];
-        const highlighted = getLanguage(language) ?
-          highlight(language, node.value).value :
-          node.value;
-        const highlightedHTML =
+        const highlighted =
           `<code class='language-${node.lang} ${node.meta}'>` +
-          highlighted +
+          (getLanguage(node.lang || '') ?
+            highlight(node.lang, node.value) : node).value +
           '</code>';
         node.type = 'html';
 
@@ -207,41 +204,32 @@ function preprocessElements({ filename }) {
             console.warn(
               `Unknown JavaScript flavor in ${filename}` +
               `:${node.position.start.line}:${node.position.start.column}`);
-            node.value = `<pre>${highlightedHTML}</pre>`;
+            node.value = `<pre>${highlighted}</pre>`;
             node.meta = null;
           } else if (!isJSFlavorSnippet(previousNode) &&
-                     !isJSFlavorSnippet(nextNode)) {
-            console.warn(
-              `JavaScript flavored blocks should go in pairs in ${filename}` +
-              `:${node.position.start.line}:${node.position.start.column}`);
-            node.value = `<pre>${highlightedHTML}</pre>`;
-            node.meta = null;
-          } else if (!isJSFlavorSnippet(previousNode) &&
-                     isJSFlavorSnippet(nextNode)) {
-            node.value = highlightedHTML;
-          } else if (node.meta === previousNode.meta) {
-            console.warn(
-              'Cannot bundle two JavaScript blocks of the same flavor in ' +
-              filename +
-              `:${node.position.start.line}:${node.position.start.column}`);
-            node.value = `<pre>${highlightedHTML}</pre>`;
-            node.meta = null;
-            previousNode.value = `<pre>${previousNode.value}</pre>`;
-            previousNode.meta = null;
-          } else {
+                     isJSFlavorSnippet(nextNode) &&
+                     nextNode.meta !== node.meta) {
+            node.value = highlighted;
+          } else if (isJSFlavorSnippet(previousNode)) {
             node.value = '<pre>' +
               '<input class="js-flavor-selector" type="checkbox"' +
               (node.meta === 'cjs' ? ' checked' : '') +
               ' aria-label="Show modern ES modules syntax">' +
               previousNode.value +
-              highlightedHTML +
+              highlighted +
               '</pre>';
             node.meta = null;
             previousNode.value = '';
             previousNode.meta = null;
+          } else {
+            console.warn(
+              `Unused JavaScript flavored block in ${filename}` +
+              `:${node.position.start.line}:${node.position.start.column}`);
+            node.value = `<pre>${highlighted}</pre>`;
+            node.meta = null;
           }
         } else {
-          node.value = `<pre>${highlightedHTML}</pre>`;
+          node.value = `<pre>${highlighted}</pre>`;
         }
       } else if (node.type === 'html' && common.isYAMLBlock(node.value)) {
         node.value = parseYAML(node.value);