diff --git a/lib/highlight.js b/lib/highlight.js
index 132004d3..b267fbaa 100644
--- a/lib/highlight.js
+++ b/lib/highlight.js
@@ -85,15 +85,7 @@ function formatLine(line, lineno, marked, options, wrap) {
 }
 
 function replaceTabs(str, tab) {
-  return str.replace(/^\t+/, match => {
-    let result = '';
-
-    for (let i = 0, len = match.length; i < len; i++) {
-      result += tab;
-    }
-
-    return result;
-  });
+  return str.replace(/\t+/, match => tab.repeat(match.length));
 }
 
 function highlight(str, options) {
diff --git a/lib/prism.js b/lib/prism.js
index 7201f2ca..c6ed45ce 100644
--- a/lib/prism.js
+++ b/lib/prism.js
@@ -41,15 +41,7 @@ function lineNumberUtil(code) {
 }
 
 function replaceTabs(str, tab) {
-  return str.replace(/^\t+/gm, match => {
-    let result = '';
-
-    for (let i = 0, len = match.length; i < len; i++) {
-      result += tab;
-    }
-
-    return result;
-  });
+  return str.replace(/^\t+/gm, match => tab.repeat(match.length));
 }
 
 function PrismUtil(str, options = {}) {
diff --git a/test/highlight.spec.js b/test/highlight.spec.js
index 86442389..6e215c0e 100644
--- a/test/highlight.spec.js
+++ b/test/highlight.spec.js
@@ -145,7 +145,7 @@ describe('highlight', () => {
       '<pre><code class="hljs json">',
       hljs.highlight(testString, {
         language: 'json'
-      }).value.replace('{', '<mark>{</mark>'),
+      }).value.replace('<span class="hljs-punctuation">{</span>', '<mark><span class="hljs-punctuation">{</span></mark>'),
       '</code></pre>'
     ].join(''));
     validateHtmlAsync(result, done);
@@ -290,12 +290,21 @@ describe('highlight', () => {
     result.should.eql([
       '<figure class="highlight php-template"><table><tr>',
       gutter(1, 1),
-      code('<span class="xml"><span class="tag">&lt;<span class="name">node</span>&gt;</span></span><span class="php"><span class="meta">&lt;?php</span> <span class="keyword">echo</span> <span class="string">&quot;foo&quot;</span>; <span class="meta">?&gt;</span></span><span class="xml"><span class="tag">&lt;/<span class="name">node</span>&gt;</span></span>', null),
+      code('<span class="language-xml"><span class="tag">&lt;<span class="name">node</span>&gt;</span></span><span class="language-php"><span class="meta">&lt;?php</span> <span class="keyword">echo</span> <span class="string">&quot;foo&quot;</span>; <span class="meta">?&gt;</span></span><span class="language-xml"><span class="tag">&lt;/<span class="name">node</span>&gt;</span></span>', null),
       end
     ].join(''));
     validateHtmlAsync(result, done);
   });
 
+  // https://github.com/hexojs/hexo/issues/4726
+  it('highlight sublanguages with tab', done => {
+    const spaces = '  ';
+    const str = '<script>\n\tfunction a() {\n\t\treturn;\n\t}\n</script>';
+    const result = highlight(str, { tab: spaces, autoDetect: true });
+    result.should.not.include('\t');
+    validateHtmlAsync(result, done);
+  });
+
   it('parse multi-line strings correctly', done => {
     const str = [
       'var string = `',
@@ -383,7 +392,7 @@ describe('highlight', () => {
     result.should.include(gutterStart);
     result.should.include(codeStart);
     result.should.include('code class="hljs javascript"');
-    result.should.include('class="hljs-function"');
+    result.should.include('class="hljs-keyword"');
     result.should.include(gutter(1, 5));
     validateHtmlAsync(result, done);
   });
@@ -400,7 +409,7 @@ describe('highlight', () => {
     result.should.not.include(gutterStart);
     result.should.not.include(codeStart);
     result.should.include('code class="hljs javascript"');
-    result.should.include('class="hljs-function"');
+    result.should.include('class="hljs-keyword"');
     validateHtmlAsync(result, done);
   });
 
@@ -416,7 +425,7 @@ describe('highlight', () => {
     result.should.not.include(gutterStart);
     result.should.include(codeStart);
     result.should.include('code class="hljs javascript"');
-    result.should.include('class="hljs-function"');
+    result.should.include('class="hljs-keyword"');
     validateHtmlAsync(result, done);
   });
 });