diff --git a/lib/consolidate.js b/lib/consolidate.js
index 02325a9..0b8d60b 100644
--- a/lib/consolidate.js
+++ b/lib/consolidate.js
@@ -81,24 +81,24 @@ function cache(options, compiled) {
  * is true the template string will be cached.
  *
  * @param {String} options
- * @param {Function} fn
+ * @param {Function} cb
  * @api private
  */
 
-function read(path, options, fn) {
+function read(path, options, cb) {
   var str = readCache[path];
   var cached = options.cache && str && typeof str === 'string';
 
   // cached (only if cached is a string and not a compiled template function)
-  if (cached) return fn(null, str);
+  if (cached) return cb(null, str);
 
   // read
   fs.readFile(path, 'utf8', function(err, str) {
-    if (err) return fn(err);
+    if (err) return cb(err);
     // remove extraneous utf8 BOM marker
     str = str.replace(/^\uFEFF/, '');
     if (options.cache) readCache[path] = str;
-    fn(null, str);
+    cb(null, str);
   });
 }
 
@@ -112,13 +112,13 @@ function read(path, options, fn) {
  * @api private
  */
 
-function readPartials(path, options, fn) {
-  if (!options.partials) return fn();
+function readPartials(path, options, cb) {
+  if (!options.partials) return cb();
   var partials = options.partials;
   var keys = Object.keys(partials);
 
   function next(index) {
-    if (index === keys.length) return fn(null);
+    if (index === keys.length) return cb(null);
     var key = keys[index];
     var partialPath = partials[key];
 
@@ -138,7 +138,7 @@ function readPartials(path, options, fn) {
     }
 
     read(file, options, function(err, str) {
-      if (err) return fn(err);
+      if (err) return cb(err);
       options.partials[key] = str;
       next(++index);
     });
@@ -150,15 +150,15 @@ function readPartials(path, options, fn) {
 /**
  * promisify
  */
-function promisify(fn, exec) {
-  return new Promise(function(res, rej) {
-    fn = fn || function(err, html) {
+function promisify(cb, fn) {
+  return new Promise(function(resolve, reject) {
+    cb = cb || function(err, html) {
       if (err) {
-        return rej(err);
+        return reject(err);
       }
-      res(html);
+      resolve(html);
     };
-    exec(fn);
+    fn(cb);
   });
 }
 
@@ -167,18 +167,18 @@ function promisify(fn, exec) {
  */
 
 function fromStringRenderer(name) {
-  return function(path, options, fn) {
+  return function(path, options, cb) {
     options.filename = path;
 
-    return promisify(fn, function(fn) {
+    return promisify(cb, function(cb) {
       readPartials(path, options, function(err) {
-        if (err) return fn(err);
+        if (err) return cb(err);
         if (cache(options)) {
-          exports[name].render('', options, fn);
+          exports[name].render('', options, cb);
         } else {
           read(path, options, function(err, str) {
-            if (err) return fn(err);
-            exports[name].render(str, options, fn);
+            if (err) return cb(err);
+            exports[name].render(str, options, cb);
           });
         }
       });
@@ -196,14 +196,14 @@ exports.velocityjs = fromStringRenderer('velocityjs');
  * velocity string support.
  */
 
-exports.velocityjs.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.velocityjs.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.velocityjs || (requires.velocityjs = require('velocityjs'));
     try {
       options.locals = options;
-      fn(null, engine.render(str, options).trimLeft());
+      cb(null, engine.render(str, options).trimLeft());
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -226,7 +226,7 @@ exports.liquid = fromStringRenderer('liquid');
  * `includeDir` will also become a local.
  */
 
-function _renderTinyliquid(engine, str, options, fn) {
+function _renderTinyliquid(engine, str, options, cb) {
   var context = engine.newContext();
   var k;
 
@@ -313,11 +313,11 @@ function _renderTinyliquid(engine, str, options, fn) {
    */
 
   var tmpl = cache(context) || cache(context, engine.compile(str, compileOptions));
-  tmpl(context, fn);
+  tmpl(context, cb);
 }
 
-exports.liquid.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.liquid.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.liquid;
     var Liquid;
 
@@ -326,7 +326,7 @@ exports.liquid.render = function(str, options, fn) {
       engine = requires.liquid = require('tinyliquid');
 
       // use tinyliquid engine
-      _renderTinyliquid(engine, str, options, fn);
+      _renderTinyliquid(engine, str, options, cb);
 
       return;
 
@@ -401,12 +401,12 @@ exports.liquid.render = function(str, options, fn) {
           if (err) {
             throw new Error(err);
           } else {
-            return fn(null, result);
+            return cb(null, result);
           }
         });
 
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -415,8 +415,8 @@ exports.liquid.render = function(str, options, fn) {
  * Jade support.
  */
 
-exports.jade = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.jade = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.jade;
     if (!engine) {
       try {
@@ -432,9 +432,9 @@ exports.jade = function(path, options, fn) {
 
     try {
       var tmpl = cache(options) || cache(options, engine.compileFile(path, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -443,8 +443,8 @@ exports.jade = function(path, options, fn) {
  * Jade string support.
  */
 
-exports.jade.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.jade.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.jade;
     if (!engine) {
       try {
@@ -460,9 +460,9 @@ exports.jade.render = function(str, options, fn) {
 
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -477,8 +477,8 @@ exports.dust = fromStringRenderer('dust');
  * Dust string support.
  */
 
-exports.dust.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.dust.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.dust;
     if (!engine) {
       try {
@@ -515,9 +515,9 @@ exports.dust.render = function(str, options, fn) {
       }
 
       var tmpl = cache(options) || cache(options, engine.compileFn(str, templateName));
-      tmpl(options, fn);
+      tmpl(options, cb);
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -532,8 +532,8 @@ exports.swig = fromStringRenderer('swig');
  * Swig string support.
  */
 
-exports.swig.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.swig.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.swig;
     if (!engine) {
       try {
@@ -551,9 +551,9 @@ exports.swig.render = function(str, options, fn) {
       if (options.cache === true) options.cache = 'memory';
       engine.setDefaults({ cache: options.cache });
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -568,14 +568,14 @@ exports.atpl = fromStringRenderer('atpl');
  * Atpl string support.
  */
 
-exports.atpl.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.atpl.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.atpl || (requires.atpl = require('atpl'));
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -590,14 +590,14 @@ exports.liquor = fromStringRenderer('liquor');
  * Liquor string support.
  */
 
-exports.liquor.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.liquor.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.liquor || (requires.liquor = require('liquor'));
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -612,17 +612,17 @@ exports.twig = fromStringRenderer('twig');
  * Twig string support.
  */
 
-exports.twig.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.twig.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.twig || (requires.twig = require('twig').twig);
     var templateData = {
       data: str
     };
     try {
       var tmpl = cache(templateData) || cache(templateData, engine(templateData));
-      fn(null, tmpl.render(options));
+      cb(null, tmpl.render(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -637,14 +637,14 @@ exports.ejs = fromStringRenderer('ejs');
  * EJS string support.
  */
 
-exports.ejs.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.ejs.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.ejs || (requires.ejs = require('ejs'));
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -659,13 +659,13 @@ exports.eco = fromStringRenderer('eco');
  * Eco string support.
  */
 
-exports.eco.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.eco.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.eco || (requires.eco = require('eco'));
     try {
-      fn(null, engine.render(str, options));
+      cb(null, engine.render(str, options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -680,16 +680,16 @@ exports.jazz = fromStringRenderer('jazz');
  * Jazz string support.
  */
 
-exports.jazz.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.jazz.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.jazz || (requires.jazz = require('jazz'));
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
       tmpl.eval(options, function(str) {
-        fn(null, str);
+        cb(null, str);
       });
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -704,14 +704,14 @@ exports.jqtpl = fromStringRenderer('jqtpl');
  * JQTPL string support.
  */
 
-exports.jqtpl.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.jqtpl.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.jqtpl || (requires.jqtpl = require('jqtpl'));
     try {
       engine.template(str, str);
-      fn(null, engine.tmpl(str, options));
+      cb(null, engine.tmpl(str, options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -726,14 +726,14 @@ exports.haml = fromStringRenderer('haml');
  * Haml string support.
  */
 
-exports.haml.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.haml.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.haml || (requires.haml = require('hamljs'));
     try {
       options.locals = options;
-      fn(null, engine.render(str, options).trimLeft());
+      cb(null, engine.render(str, options).trimLeft());
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -748,14 +748,14 @@ exports.hamlet = fromStringRenderer('hamlet');
  * Hamlet string support.
  */
 
-exports.hamlet.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.hamlet.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.hamlet || (requires.hamlet = require('hamlet'));
     try {
       options.locals = options;
-      fn(null, engine.render(str, options).trimLeft());
+      cb(null, engine.render(str, options).trimLeft());
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -764,10 +764,10 @@ exports.hamlet.render = function(str, options, fn) {
  * Whiskers support.
  */
 
-exports.whiskers = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.whiskers = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.whiskers || (requires.whiskers = require('whiskers'));
-    engine.__express(path, options, fn);
+    engine.__express(path, options, cb);
   });
 };
 
@@ -775,13 +775,13 @@ exports.whiskers = function(path, options, fn) {
  * Whiskers string support.
  */
 
-exports.whiskers.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.whiskers.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.whiskers || (requires.whiskers = require('whiskers'));
     try {
-      fn(null, engine.render(str, options));
+      cb(null, engine.render(str, options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -796,14 +796,14 @@ exports['haml-coffee'] = fromStringRenderer('haml-coffee');
  * Coffee-HAML string support.
  */
 
-exports['haml-coffee'].render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports['haml-coffee'].render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires['haml-coffee'] || (requires['haml-coffee'] = require('haml-coffee'));
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -818,14 +818,14 @@ exports.hogan = fromStringRenderer('hogan');
  * Hogan string support.
  */
 
-exports.hogan.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.hogan.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.hogan || (requires.hogan = require('hogan.js'));
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl.render(options, options.partials));
+      cb(null, tmpl.render(options, options.partials));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -840,14 +840,14 @@ exports.templayed = fromStringRenderer('templayed');
  * templayed.js string support.
  */
 
-exports.templayed.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.templayed.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.templayed || (requires.templayed = require('templayed'));
     try {
       var tmpl = cache(options) || cache(options, engine(str));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -862,8 +862,8 @@ exports.handlebars = fromStringRenderer('handlebars');
  * Handlebars string support.
  */
 
-exports.handlebars.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.handlebars.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.handlebars || (requires.handlebars = require('handlebars'));
     try {
       for (var partial in options.partials) {
@@ -873,9 +873,9 @@ exports.handlebars.render = function(str, options, fn) {
         engine.registerHelper(helper, options.helpers[helper]);
       }
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -890,17 +890,17 @@ exports.underscore = fromStringRenderer('underscore');
  * Underscore string support.
  */
 
-exports.underscore.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.underscore.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.underscore || (requires.underscore = require('underscore'));
     try {
       for (var partial in options.partials) {
         options.partials[partial] = engine.template(options.partials[partial]);
       }
       var tmpl = cache(options) || cache(options, engine.template(str, null, options));
-      fn(null, tmpl(options).replace(/\n$/, ''));
+      cb(null, tmpl(options).replace(/\n$/, ''));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -915,14 +915,14 @@ exports.lodash = fromStringRenderer('lodash');
  * Lodash string support.
  */
 
-exports.lodash.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.lodash.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.lodash || (requires.lodash = require('lodash'));
     try {
       var tmpl = cache(options) || cache(options, engine.template(str, options));
-      fn(null, tmpl(options).replace(/\n$/, ''));
+      cb(null, tmpl(options).replace(/\n$/, ''));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -931,8 +931,8 @@ exports.lodash.render = function(str, options, fn) {
  * Pug support. (formerly Jade)
  */
 
-exports.pug = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.pug = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.pug;
     if (!engine) {
       try {
@@ -948,9 +948,9 @@ exports.pug = function(path, options, fn) {
 
     try {
       var tmpl = cache(options) || cache(options, engine.compileFile(path, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -959,8 +959,8 @@ exports.pug = function(path, options, fn) {
  * Pug string support.
  */
 
-exports.pug.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.pug.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.pug;
     if (!engine) {
       try {
@@ -976,9 +976,9 @@ exports.pug.render = function(str, options, fn) {
 
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -993,17 +993,17 @@ exports.qejs = fromStringRenderer('qejs');
  * QEJS string support.
  */
 
-exports.qejs.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.qejs.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     try {
       var engine = requires.qejs || (requires.qejs = require('qejs'));
       engine.render(str, options).then(function(result) {
-        fn(null, result);
+        cb(null, result);
       }, function(err) {
-        fn(err);
+        cb(err);
       }).done();
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1018,14 +1018,14 @@ exports.walrus = fromStringRenderer('walrus');
  * Walrus string support.
  */
 
-exports.walrus.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.walrus.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.walrus || (requires.walrus = require('walrus'));
     try {
       var tmpl = cache(options) || cache(options, engine.parse(str));
-      fn(null, tmpl.compile(options));
+      cb(null, tmpl.compile(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1040,13 +1040,13 @@ exports.mustache = fromStringRenderer('mustache');
  * Mustache string support.
  */
 
-exports.mustache.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.mustache.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.mustache || (requires.mustache = require('mustache'));
     try {
-      fn(null, engine.to_html(str, options, options.partials));
+      cb(null, engine.to_html(str, options, options.partials));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1055,15 +1055,15 @@ exports.mustache.render = function(str, options, fn) {
  * Just support.
  */
 
-exports.just = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.just = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.just;
     if (!engine) {
       var JUST = require('just');
       engine = requires.just = new JUST();
     }
     engine.configure({ useCache: options.cache });
-    engine.render(path, options, fn);
+    engine.render(path, options, cb);
   });
 };
 
@@ -1071,11 +1071,11 @@ exports.just = function(path, options, fn) {
  * Just string support.
  */
 
-exports.just.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.just.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var JUST = require('just');
     var engine = new JUST({ root: { page: str }});
-    engine.render('page', options, fn);
+    engine.render('page', options, cb);
   });
 };
 
@@ -1083,15 +1083,15 @@ exports.just.render = function(str, options, fn) {
  * ECT support.
  */
 
-exports.ect = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.ect = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.ect;
     if (!engine) {
       var ECT = require('ect');
       engine = requires.ect = new ECT(options);
     }
     engine.configure({ cache: options.cache });
-    engine.render(path, options, fn);
+    engine.render(path, options, cb);
   });
 };
 
@@ -1099,11 +1099,11 @@ exports.ect = function(path, options, fn) {
  * ECT string support.
  */
 
-exports.ect.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.ect.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var ECT = require('ect');
     var engine = new ECT({ root: { page: str }});
-    engine.render('page', options, fn);
+    engine.render('page', options, cb);
   });
 };
 
@@ -1117,14 +1117,14 @@ exports.mote = fromStringRenderer('mote');
  * mote string support.
  */
 
-exports.mote.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.mote.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.mote || (requires.mote = require('mote'));
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1133,10 +1133,10 @@ exports.mote.render = function(str, options, fn) {
  * Toffee support.
  */
 
-exports.toffee = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.toffee = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var toffee = requires.toffee || (requires.toffee = require('toffee'));
-    toffee.__consolidate_engine_render(path, options, fn);
+    toffee.__consolidate_engine_render(path, options, cb);
   });
 };
 
@@ -1144,13 +1144,13 @@ exports.toffee = function(path, options, fn) {
  * Toffee string support.
  */
 
-exports.toffee.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.toffee.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.toffee || (requires.toffee = require('toffee'));
     try {
-      engine.str_render(str, options, fn);
+      engine.str_render(str, options, cb);
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1165,8 +1165,8 @@ exports.dot = fromStringRenderer('dot');
  * doT string support.
  */
 
-exports.dot.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.dot.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.dot || (requires.dot = require('dot'));
     var extend = (requires.extend || (requires.extend = require('util')._extend));
     try {
@@ -1174,9 +1174,9 @@ exports.dot.render = function(str, options, fn) {
       settings = extend(settings, engine.templateSettings);
       settings = extend(settings, options ? options.dot : {});
       var tmpl = cache(options) || cache(options, engine.template(str, settings, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1191,14 +1191,14 @@ exports.bracket = fromStringRenderer('bracket');
  * bracket string support.
  */
 
-exports.bracket.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.bracket.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.bracket || (requires.bracket = require('bracket-template'));
     try {
       var tmpl = cache(options) || cache(options, engine.default.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1213,8 +1213,8 @@ exports.ractive = fromStringRenderer('ractive');
  * Ractive string support.
  */
 
-exports.ractive.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.ractive.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var Engine = requires.ractive || (requires.ractive = require('ractive'));
 
     var template = cache(options) || cache(options, Engine.parse(str));
@@ -1237,9 +1237,9 @@ exports.ractive.render = function(str, options, fn) {
     }
 
     try {
-      fn(null, new Engine(options).toHTML());
+      cb(null, new Engine(options).toHTML());
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1254,8 +1254,8 @@ exports.nunjucks = fromStringRenderer('nunjucks');
  * Nunjucks string support.
  */
 
-exports.nunjucks.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.nunjucks.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
 
     try {
 
@@ -1266,7 +1266,11 @@ exports.nunjucks.render = function(str, options, fn) {
       // deprecated fallback support for express
       // <https://github.com/tj/consolidate.js/pull/152>
       // <https://github.com/tj/consolidate.js/pull/224>
-      if (options.settings && options.settings.views) { env = engine.configure(options.settings.views); } else if (options.nunjucks && options.nunjucks.configure) { env = engine.configure.apply(engine, options.nunjucks.configure); }
+      if (options.settings && options.settings.views) {
+        env = engine.configure(options.settings.views);
+      } else if (options.nunjucks && options.nunjucks.configure) {
+        env = engine.configure.apply(engine, options.nunjucks.configure);
+      }
 
       //
       // because `renderString` does not initiate loaders
@@ -1277,21 +1281,6 @@ exports.nunjucks.render = function(str, options, fn) {
       // <https://github.com/crocodilejs/node-email-templates/issues/182>
       //
 
-      //
-      // note that the below code didn't work nor make sense before
-      // because loaders should take different options from rendering
-      //
-
-      /*
-      var loader = options.loader;
-      if (loader) {
-        var env = new engine.Environment(new loader(options));
-        env.renderString(str, options, fn);
-      } else {
-        engine.renderString(str, options, fn);
-      }
-      */
-
       // so instead we simply check if we passed a custom loader
       // otherwise we create a simple file based loader
       if (options.loader) {
@@ -1301,7 +1290,9 @@ exports.nunjucks.render = function(str, options, fn) {
           new engine.FileSystemLoader(options.settings.views)
         );
       } else if (options.nunjucks && options.nunjucks.loader) {
-        if (typeof options.nunjucks.loader === 'string') { env = new engine.Environment(new engine.FileSystemLoader(options.nunjucks.loader)); } else {
+        if (typeof options.nunjucks.loader === 'string') {
+          env = new engine.Environment(new engine.FileSystemLoader(options.nunjucks.loader));
+        } else {
           env = new engine.Environment(
             new engine.FileSystemLoader(
               options.nunjucks.loader[0],
@@ -1311,10 +1302,9 @@ exports.nunjucks.render = function(str, options, fn) {
         }
       }
 
-      env.renderString(str, options, fn);
-
+      env.renderString(str, options, cb);
     } catch (err) {
-      throw fn(err);
+      throw cb(err);
     }
   });
 };
@@ -1329,14 +1319,14 @@ exports.htmling = fromStringRenderer('htmling');
  * HTMLing string support.
  */
 
-exports.htmling.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.htmling.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.htmling || (requires.htmling = require('htmling'));
     try {
       var tmpl = cache(options) || cache(options, engine.string(str));
-      fn(null, tmpl.render(options));
+      cb(null, tmpl.render(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1407,15 +1397,15 @@ exports.plates = fromStringRenderer('plates');
 * Plates string support.
 */
 
-exports.plates.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.plates.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.plates || (requires.plates = require('plates'));
     var map = options.map || undefined;
     try {
       var tmpl = engine.bind(str, options, map);
-      fn(null, tmpl);
+      cb(null, tmpl);
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1441,8 +1431,8 @@ function reactRenderer(type) {
   }
 
   // Return rendering fx
-  return function(str, options, fn) {
-    return promisify(fn, function(fn) {
+  return function(str, options, cb) {
+    return promisify(cb, function(cb) {
       // React Import
       var ReactDOM = requires.ReactDOM || (requires.ReactDOM = require('react-dom/server'));
       var react = requires.react || (requires.react = require('react'));
@@ -1496,10 +1486,10 @@ function reactRenderer(type) {
           content = reactBaseTmpl(baseStr, options);
         }
 
-        fn(null, content);
+        cb(null, content);
 
       } catch (err) {
-        fn(err);
+        cb(err);
       }
     });
   };
@@ -1525,14 +1515,14 @@ exports['arc-templates'] = fromStringRenderer('arc-templates');
  * ARC-templates string support.
  */
 
-exports['arc-templates'].render = function(str, options, fn) {
+exports['arc-templates'].render = function(str, options, cb) {
   var readFileWithOptions = Promise.promisify(read);
   var consolidateFileSystem = {};
   consolidateFileSystem.readFile = function(path) {
     return readFileWithOptions(path, options);
   };
 
-  return promisify(fn, function(fn) {
+  return promisify(cb, function(cb) {
     try {
       var engine = requires['arc-templates'];
       if (!engine) {
@@ -1542,10 +1532,10 @@ exports['arc-templates'].render = function(str, options, fn) {
 
       var compiler = cache(options) || cache(options, engine.compileString(str, options.filename));
       compiler.then(function(func) { return func(options); })
-        .then(function(result) { fn(null, result.content); })
-        .catch(fn);
+        .then(function(result) { cb(null, result.content); })
+        .catch(cb);
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1558,8 +1548,8 @@ exports.vash = fromStringRenderer('vash');
 /**
  * Vash string support
  */
-exports.vash.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.vash.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.vash || (requires.vash = require('vash'));
 
     try {
@@ -1575,12 +1565,12 @@ exports.vash.render = function(str, options, fn) {
 
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
       tmpl(options, function sealLayout(err, ctx) {
-        if (err) fn(err);
+        if (err) cb(err);
         ctx.finishLayout();
-        fn(null, ctx.toString().replace(/\n$/, ''));
+        cb(null, ctx.toString().replace(/\n$/, ''));
       });
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1595,15 +1585,15 @@ exports.slm = fromStringRenderer('slm');
  * Slm string support.
  */
 
-exports.slm.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.slm.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.slm || (requires.slm = require('slm'));
 
     try {
       var tmpl = cache(options) || cache(options, engine.compile(str, options));
-      fn(null, tmpl(options));
+      cb(null, tmpl(options));
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1612,16 +1602,16 @@ exports.slm.render = function(str, options, fn) {
  * Marko support.
  */
 
-exports.marko = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.marko = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.marko || (requires.marko = require('marko'));
     options.writeToDisk = !!options.cache;
 
     try {
       var tmpl = cache(options) || cache(options, engine.load(path, options));
-      tmpl.renderToString(options, fn);
+      tmpl.renderToString(options, cb);
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1630,17 +1620,17 @@ exports.marko = function(path, options, fn) {
  * Marko string support.
  */
 
-exports.marko.render = function(str, options, fn) {
-  return promisify(fn, function(fn) {
+exports.marko.render = function(str, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.marko || (requires.marko = require('marko'));
     options.writeToDisk = !!options.cache;
     options.filename = options.filename || 'string.marko';
 
     try {
       var tmpl = cache(options) || cache(options, engine.load(options.filename, str, options));
-      tmpl.renderToString(options, fn);
+      tmpl.renderToString(options, cb);
     } catch (err) {
-      fn(err);
+      cb(err);
     }
   });
 };
@@ -1648,38 +1638,38 @@ exports.marko.render = function(str, options, fn) {
 /**
  * Teacup support.
  */
-exports.teacup = function(path, options, fn) {
-  return promisify(fn, function(fn) {
+exports.teacup = function(path, options, cb) {
+  return promisify(cb, function(cb) {
     var engine = requires.teacup || (requires.teacup = require('teacup/lib/express'));
     require.extensions['.teacup'] = require.extensions['.coffee'];
     if (path[0] !== '/') {
       path = join(process.cwd(), path);
     }
     if (!options.cache) {
-      var originalFn = fn;
-      fn = function() {
+      var callback = cb;
+      cb = function() {
         delete require.cache[path];
-        originalFn.apply(this, arguments);
+        callback.apply(this, arguments);
       };
     }
-    engine.renderFile(path, options, fn);
+    engine.renderFile(path, options, cb);
   });
 };
 
 /**
  * Teacup string support.
  */
-exports.teacup.render = function(str, options, fn) {
+exports.teacup.render = function(str, options, cb) {
   var coffee = require('coffee-script');
   var vm = require('vm');
   var sandbox = {
     module: {exports: {}},
     require: require
   };
-  return promisify(fn, function(fn) {
+  return promisify(cb, function(cb) {
     vm.runInNewContext(coffee.compile(str), sandbox);
     var tmpl = sandbox.module.exports;
-    fn(null, tmpl(options));
+    cb(null, tmpl(options));
   });
 };
 
diff --git a/package.json b/package.json
index 5918554..c4bef6d 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,7 @@
   ],
   "main": "index.js",
   "engines": {
-    "node": ">= 4.0"
+    "node": ">= 0.10.0"
   },
   "scripts": {
     "lint": "eslint .",