diff --git a/js/moz-parser.js b/js/moz-parser.js
index 28b07819..7d52d495 100644
--- a/js/moz-parser.js
+++ b/js/moz-parser.js
@@ -1,7 +1,15 @@
 /* global parserlib */
 'use strict';
 
-function parseMozFormat(mozStyle) {
+/**
+ * Extracts @-moz-document blocks into sections and the code between them into global sections.
+ * Puts the global comments into the following section to minimize the amount of global sections.
+ * Doesn't move the comment with ==UserStyle== inside.
+ * @param {string} code
+ * @param {number} styleId - used to preserve parserCache on subsequent runs over the same style
+ * @returns {{sections: Array, errors: Array}}
+ */
+function parseMozFormat({code, styleId}) {
   const CssToProperty = {
     'url':        'urls',
     'url-prefix': 'urlPrefixes',
@@ -12,6 +20,7 @@ function parseMozFormat(mozStyle) {
   const sectionStack = [{code: '', start: 0}];
   const errors = [];
   const sections = [];
+  const mozStyle = code;
 
   parser.addListener('startdocument', e => {
     const lastSection = sectionStack[sectionStack.length - 1];
@@ -62,7 +71,10 @@ function parseMozFormat(mozStyle) {
     errors.push(`${e.line}:${e.col} ${e.message.replace(/ at line \d.+$/, '')}`);
   });
 
-  parser.parse(mozStyle);
+  parser.parse(mozStyle, {
+    reuseCache: !parseMozFormat.styleId || styleId === parseMozFormat.styleId,
+  });
+  parseMozFormat.styleId = styleId;
   return {sections, errors};
 
   function doAddSection(section) {
diff --git a/js/usercss.js b/js/usercss.js
index 340136e1..59233dcc 100644
--- a/js/usercss.js
+++ b/js/usercss.js
@@ -489,7 +489,11 @@ var usercss = (() => {
       Promise.resolve(
         builder.preprocess && builder.preprocess(sourceCode, sVars) ||
         sourceCode)
-      .then(mozStyle => invokeWorker({action: 'parse', code: mozStyle}))
+      .then(mozStyle => invokeWorker({
+        action: 'parse',
+        styleId: style.id,
+        code: mozStyle,
+      }))
       .then(({sections, errors}) => sections.length && sections || Promise.reject(errors))
       .then(sections => {
         style.sections = sections;
diff --git a/vendor-overwrites/csslint/csslint-loader.js b/vendor-overwrites/csslint/csslint-loader.js
index 89788180..54776d57 100644
--- a/vendor-overwrites/csslint/csslint-loader.js
+++ b/vendor-overwrites/csslint/csslint-loader.js
@@ -4,13 +4,16 @@
 self.importScripts('./parserlib.js');
 parserlib.css.Tokens[parserlib.css.Tokens.COMMENT].hide = false;
 
-self.onmessage = ({data: {action = 'run', code, config}}) => {
+self.onmessage = ({data}) => {
+
+  const {action = 'run'} = data;
 
   if (action === 'parse') {
     if (!self.parseMozFormat) self.importScripts('/js/moz-parser.js');
-    self.postMessage(parseMozFormat(code));
+    self.postMessage(parseMozFormat(data));
     return;
   }
+
   if (!self.CSSLint) self.importScripts('./csslint.js');
 
   switch (action) {
@@ -25,6 +28,7 @@ self.onmessage = ({data: {action = 'run', code, config}}) => {
       return;
 
     case 'run': {
+      const {code, config} = data;
       const results = CSSLint.verify(code, config).messages
         //.filter(m => !m.message.includes('/*[[') && !m.message.includes(']]*/'))
         .map(m => Object.assign(m, {rule: {id: m.rule.id}}));
diff --git a/vendor-overwrites/csslint/parserlib.js b/vendor-overwrites/csslint/parserlib.js
index aa722c1f..51d1370e 100644
--- a/vendor-overwrites/csslint/parserlib.js
+++ b/vendor-overwrites/csslint/parserlib.js
@@ -1467,10 +1467,15 @@ self.parserlib = (() => {
      */
     function start(newParser) {
       parser = newParser;
-      if (!parser) return;
+      if (!parser) {
+        data.clear();
+        stack.length = 0;
+        generationBase = performance.now();
+        return;
+      }
       if (firstRun) firstRun = false;
       stream = parser._tokenStream;
-      generation = generationBase = performance.now();
+      generation = performance.now();
       trim();
     }