diff --git a/index.js b/index.js
index 62fbcc5..113053e 100644
--- a/index.js
+++ b/index.js
@@ -4,6 +4,7 @@
 
 var fs = require('fs');
 var Decoder = require('pull-utf8-decoder')
+var Lock = require('lock')
 /**
   # pull-file
 
@@ -25,6 +26,7 @@ module.exports = function(filename, opts) {
 
   var ended, closeNext, busy;
   var _buffer = new Buffer(bufferSize)
+  var lock = Lock()
   var live = opts && !!opts.live
   var liveCb, closeCb
   var watcher
@@ -78,10 +80,12 @@ module.exports = function(filename, opts) {
           return cb(err);
         }
 
-        if(count === buffer.length) {
+        if(count === toRead && count === buffer.length) {
           cb(null, buffer);
         } else if(count === 0 && live) {
           liveCb = cb; closeNext = true
+        } else if (count === 0) {
+          cb(ended = true)
         } else {
           closeNext = true;
           cb(null, buffer.slice(0, count));
@@ -161,11 +165,16 @@ module.exports = function(filename, opts) {
       readNext(cb);
   };
 
+  var lockedSource = function (end, cb) {
+    lock('source', function (release) {
+      source(end, release(cb))
+    })
+  }
+
   //read directly to text
   if(opts && opts.encoding)
-    return Decoder(opts.encoding)(source)
+    return Decoder(opts.encoding)(lockedSource)
 
-  return source
+  return lockedSource
 
 };
-
diff --git a/package.json b/package.json
index 7fd0a2d..361a8c9 100644
--- a/package.json
+++ b/package.json
@@ -34,6 +34,7 @@
   },
   "homepage": "https://github.com/DamonOehlman/pull-file",
   "dependencies": {
+    "lock": "^0.1.3",
     "pull-utf8-decoder": "^1.0.2"
   }
-}
\ No newline at end of file
+}
diff --git a/test/largefile.js b/test/largefile.js
index 1ac116e..a10988a 100644
--- a/test/largefile.js
+++ b/test/largefile.js
@@ -43,8 +43,43 @@ test('large file as ascii strings', function(t) {
   );
 });
 
+test('large file fast reads', function(t) {
+  var big = crypto.pseudoRandomBytes(10*1024*1024)
+  fs.writeFileSync(tmpfile, big)
 
+  var read = file(tmpfile, {bufferSize: 1024 * 1024})
+  var items = []
 
+  read(null, checkRead)
+  read(null, checkRead)
+  read(null, checkRead)
+  read(null, checkRead)
+  read(null, checkRead)
 
+  setTimeout(function () {
+    read(null, checkRead)
+    read(null, checkRead)
+    read(null, checkRead)
+    read(null, checkRead)
+    read(null, checkRead)
+    read(null, function (err, data) {
+      t.equal(err, true)
+      t.equal(data, undefined)
+      next()
+    })
+  }, 10)
 
+  function checkRead (err, data) {
+    t.equal(data.length, 1024 * 1024)
+    items.push(data)
+    next()
+  }
 
+  var i = 0
+  function next () {
+    if (++i === 11) {
+      t.equal(hash(big), hash(Buffer.concat(items)))
+      t.end()
+    }
+  }
+})