diff --git a/index.js b/index.js
index bfc3160..84f7a67 100644
--- a/index.js
+++ b/index.js
@@ -1,14 +1,47 @@
 const { isNull, isBoolean, isNumber, isString, isArray, isObject, isEmpty, fromPairs, keys, map, repeat } = require('lodash')
 const { parse: parseLua } = require('luaparse')
 
-const formatLuaString = (string, singleQuote) => (singleQuote ? `'${string.replace(/'/g, "\\'")}'` : `"${string.replace(/"/g, '\\"')}"`)
+/**
+ * @link https://github.com/fstirlitz/luaparse/blob/0f525b152516bc8afa34564de2423b039aa83bc1/luaparse.js#L1414
+ * @param {string} id 
+ * @returns {boolean}
+ */
+function isKeyword(id) {
+  switch (id.length) {
+    case 2:
+      return 'do' === id || 'if' === id || 'in' === id || 'or' === id;
+    case 3:
+      return 'and' === id || 'end' === id || 'for' === id || 'not' === id;
+    case 4:
+      // TODO: configure labels "goto"
+      return 'else' === id || 'then' === id || 'goto' === id;
+    case 5:
+      return 'break' === id || 'local' === id || 'until' === id || 'while' === id;
+    case 6:
+      return 'elseif' === id || 'repeat' === id || 'return' === id;
+    case 8:
+      return 'function' === id;
+  }
+  return false;
+}
+
+const formatLuaString = (string, singleQuote, multilineString) => {
+  string = string.replace(/\\/g, "\\\\")
+  if (multilineString) {
+    if(string.includes("]]")) throw new SyntaxError("Multiline string can't include ']]'.") // TODO: provide more information about the error
+    return `[[${string}]]`
+  } else {
+    string = string.replace(/\n/g, "\\n")
+    return (singleQuote ? `'${string.replace(/'/g, "\\'")}'` : `"${string.replace(/"/g, '\\"')}"`)
+  }
+}
 
 const valueKeys = { false: 'false', true: 'true', null: 'nil' }
 
 const formatLuaKey = (string, singleQuote) =>
-  valueKeys[string] ? `[${valueKeys[string]}]` : string.match(/^[a-zA-Z_][a-zA-Z_0-9]*$/) ? string : `[${formatLuaString(string, singleQuote)}]`
+  valueKeys[string] ? `[${valueKeys[string]}]` : (string.match(/^[a-zA-Z_][a-zA-Z_0-9]*$/) && !isKeyword(string)) ? string : `[${formatLuaString(string, singleQuote)}]`
 
-const format = (value, options = { eol: '\n', singleQuote: true, spaces: 2 }) => {
+const format = (value, options = { eol: '\n', singleQuote: true, multilineString: false, spaces: 2 }) => {
   options = options || {}
   const eol = (options.eol = isString(options.eol) ? options.eol : '\n')
   options.singleQuote = isBoolean(options.singleQuote) ? options.singleQuote : true
@@ -22,7 +55,7 @@ const format = (value, options = { eol: '\n', singleQuote: true, spaces: 2 }) =>
       return value.toString()
     }
     if (isString(value)) {
-      return formatLuaString(value, options.singleQuote)
+      return formatLuaString(value, options.singleQuote, options.multilineString)
     }
     if (isArray(value)) {
       if (isEmpty(value)) {
@@ -43,11 +76,11 @@ const format = (value, options = { eol: '\n', singleQuote: true, spaces: 2 }) =>
         const spaces = isNumber(options.spaces) ? repeat(' ', options.spaces * (i + 1)) : repeat(options.spaces, i + 1)
         const spacesEnd = isNumber(options.spaces) ? repeat(' ', options.spaces * i) : repeat(options.spaces, i)
         return `{${eol}${keys(value)
-          .map(key => `${spaces}${formatLuaKey(key, options.singleQuote)} = ${rec(value[key], i + 1)},`)
+          .map(key => `${spaces}${formatLuaKey(key, options.singleQuote, false)} = ${rec(value[key], i + 1)},`)
           .join(eol)}${eol}${spacesEnd}}`
       }
       return `{${keys(value)
-        .map(key => `${formatLuaKey(key, options.singleQuote)}=${rec(value[key], i + 1)},`)
+        .map(key => `${formatLuaKey(key, options.singleQuote, false)}=${rec(value[key], i + 1)},`)
         .join('')}}`
     }
     throw new Error(`can't format ${typeof value}`)
diff --git a/test.js b/test.js
index ceffaf3..cbdea86 100644
--- a/test.js
+++ b/test.js
@@ -13,6 +13,12 @@ const json = {
   _float: 3.14,
   _big: 1e123,
   _string: "...'...'...",
+  _multilinestring: '1st line\n2nd line\n3rd line',
+  _backslash: {
+    _single: '\\',
+    _double: '\\\\',
+    _followed: '\\test',
+  },
   _array0: [],
   _array1: [1],
   _array2: [1, 2],
@@ -29,6 +35,27 @@ const json = {
     false: 4,
     true: 5,
   },
+  _keywords: {
+    do: 'keyword',
+    if: 'keyword',
+    in: 'keyword',
+    or: 'keyword',
+    and: 'keyword',
+    end: 'keyword',
+    for: 'keyword',
+    not: 'keyword',
+    else: 'keyword',
+    then: 'keyword',
+    goto: 'keyword',
+    break: 'keyword',
+    local: 'keyword',
+    until: 'keyword',
+    while: 'keyword',
+    elseif: 'keyword',
+    repeat: 'keyword',
+    return: 'keyword',
+    function: 'keyword'
+  }
 }
 
 const lua = `return {
@@ -41,6 +68,12 @@ const lua = `return {
   _float = 3.14,
   _big = 1e+123,
   _string = '...\\'...\\'...',
+  _multilinestring = '1st line\\n2nd line\\n3rd line',
+  _backslash = {
+    _single = '\\\\',
+    _double = '\\\\\\\\',
+    _followed = '\\\\test',
+  },
   _array0 = {},
   _array1 = {
     1,
@@ -62,9 +95,30 @@ const lua = `return {
     [false] = 4,
     [true] = 5,
   },
+  _keywords = {
+    ['do'] = 'keyword',
+    ['if'] = 'keyword',
+    ['in'] = 'keyword',
+    ['or'] = 'keyword',
+    ['and'] = 'keyword',
+    ['end'] = 'keyword',
+    ['for'] = 'keyword',
+    ['not'] = 'keyword',
+    ['else'] = 'keyword',
+    ['then'] = 'keyword',
+    ['goto'] = 'keyword',
+    ['break'] = 'keyword',
+    ['local'] = 'keyword',
+    ['until'] = 'keyword',
+    ['while'] = 'keyword',
+    ['elseif'] = 'keyword',
+    ['repeat'] = 'keyword',
+    ['return'] = 'keyword',
+    ['function'] = 'keyword',
+  },
 }`
 
-const luaMinified = `return{_null=nil,_false=false,_true=true,_zero=0,_one=1,_negative=-1,_float=3.14,_big=1e+123,_string='...\\'...\\'...',_array0={},_array1={1,},_array2={1,2,},_object0={},_object1={_nested={_value=1,},},_object2={['a b']=1,['...\\'...\\'...']=2,[nil]=3,[false]=4,[true]=5,},}`
+const luaMinified = `return{_null=nil,_false=false,_true=true,_zero=0,_one=1,_negative=-1,_float=3.14,_big=1e+123,_string='...\\'...\\'...',_multilinestring='1st line\\n2nd line\\n3rd line',_backslash={_single='\\\\',_double='\\\\\\\\',_followed='\\\\test',},_array0={},_array1={1,},_array2={1,2,},_object0={},_object1={_nested={_value=1,},},_object2={['a b']=1,['...\\'...\\'...']=2,[nil]=3,[false]=4,[true]=5,},_keywords={['do']='keyword',['if']='keyword',['in']='keyword',['or']='keyword',['and']='keyword',['end']='keyword',['for']='keyword',['not']='keyword',['else']='keyword',['then']='keyword',['goto']='keyword',['break']='keyword',['local']='keyword',['until']='keyword',['while']='keyword',['elseif']='keyword',['repeat']='keyword',['return']='keyword',['function']='keyword',},}`
 
 equal(format(json), lua)
 deepEqual(parse(lua), json)
@@ -77,3 +131,12 @@ jsonDoubleQuote._object2 = mapKeys(jsonDoubleQuote._object2, (_, key) => key.rep
 const luaDoubleQuote = lua.replace(/'/g, '"')
 equal(format(jsonDoubleQuote, { singleQuote: false }), luaDoubleQuote)
 deepEqual(parse(luaDoubleQuote), jsonDoubleQuote)
+
+const jsonMultiline = { "test": "1st line\n2nd line\n3rd line" }
+const luaMultiline = `return {
+  test = [[1st line
+2nd line
+3rd line]],
+}`
+equal(format(jsonMultiline, { multilineString: true }), luaMultiline)
+deepEqual(parse(luaMultiline), jsonMultiline)