diff --git a/examples/low-level.js b/examples/low-level.js
index e274660..b5df695 100644
--- a/examples/low-level.js
+++ b/examples/low-level.js
@@ -20,13 +20,14 @@ curl.on('data', function(chunk) {
 curl.on('error', function(e) {
 	p("error: " + e.message)
 	curl.close();
+	once();
 });
 
 
 curl.on('end', function() {
-	p('done.');
-	p('code: ' + curl.getinfo('RESPONSE_CODE'));
+	curl.getinfo('RESPONSE_CODE');
 	curl.close();
+	p('done.');
 });
 
 curl.perform();
diff --git a/lib/Curl.js b/lib/Curl.js
index 6253d1e..1565368 100644
--- a/lib/Curl.js
+++ b/lib/Curl.js
@@ -1,6 +1,6 @@
 // Generated by ToffeeScript 1.4.0
 (function() {
-  var Curl, m, p;
+  var Curl, curls, id, m, p;
 
   try {
     Curl = require(__dirname + '/../build/Release/node-curl').Curl;
@@ -8,6 +8,10 @@
     Curl = require(__dirname + '/../build/default/node-curl').Curl;
   }
 
+  curls = {};
+
+  id = 0;
+
   Curl.prototype.setopt_user_ = function(option_id, value) {
     return this.options[option_id] = value;
   };
@@ -54,15 +58,26 @@
   };
 
   Curl.prototype.on = function(event, callback) {
+    var _this = this;
     switch (event) {
       case 'data':
         this.on_write = callback;
         break;
       case 'error':
-        this.on_error = callback;
+        this.on_error = function() {
+          var rt;
+          rt = callback();
+          curls[_this.id] = null;
+          return rt;
+        };
         break;
       case 'end':
-        this.on_end = callback;
+        this.on_end = function() {
+          var rt;
+          rt = callback();
+          curls[_this.id] = null;
+          return rt;
+        };
         break;
       default:
         throw new Error("invalid event type " + event);
@@ -71,6 +86,8 @@
   };
 
   Curl.prototype.perform = function() {
+    this.id = ++id;
+    curls[this.id] = this;
     this.perform_();
     Curl.process();
     return this;
@@ -95,7 +112,7 @@
           return process.nextTick(once);
         } else {
           m = 0;
-          w = (8192 - n) * 80 / 8192;
+          w = (8192 - n) * 80 / 8192 >> 0;
           if (w < 0) {
             w = 0;
           }
diff --git a/lib/Curl.toffee b/lib/Curl.toffee
index 69185e3..338a1ee 100644
--- a/lib/Curl.toffee
+++ b/lib/Curl.toffee
@@ -3,6 +3,8 @@ try
 catch e
   {Curl} = require __dirname + '/../build/default/node-curl'
 
+curls = {}
+id = 0
 Curl::setopt_user_ = (option_id, value) ->
   @options[option_id] = value
 
@@ -50,15 +52,24 @@ Curl::on = (event, callback) ->
       @on_write = callback
     when 'error'
       # (Error error) ->
-      @on_error = callback
+      @on_error = =>
+        rt = callback()
+        curls[@id] = null
+        rt
+
     when 'end'
       # () ->
-      @on_end = callback
+      @on_end = =>
+        rt = callback()
+        curls[@id] = null
+        rt
     else
       throw new Error("invalid event type #{event}")
   @
 
 Curl::perform = ->
+  @id = ++id
+  curls[@id] = @
   @perform_()
   Curl.process()
   @
@@ -77,7 +88,7 @@ Curl.process = ->
         process.nextTick once
       else
         m = 0
-        w = (8192 - n) * 80 / 8192
+        w = (8192 - n) * 80 / 8192 >> 0
         if w < 0
           w = 0
         setTimeout once, w
diff --git a/src/node-curl.h b/src/node-curl.h
index ea0e593..9079c2e 100644
--- a/src/node-curl.h
+++ b/src/node-curl.h
@@ -29,8 +29,6 @@ class NodeCurl
 	CURL  * curl;
 	v8::Persistent<v8::Object> handle;
 
-	// keep the object alive when performing
-	v8::Persistent<v8::Object> refer;
 	bool  in_curlm;
 	std::vector<curl_slist*> slists;
 	std::map<int, std::string> strings;
@@ -331,8 +329,7 @@ class NodeCurl
 					else
 						curl->on_error(&msg_copy);
 
-					curl->refer.Dispose();
-					curl->refer.Clear();
+					// Handle should not released in curl.process, or will cause segment fault.
 				}
 			}
 		}
@@ -343,12 +340,6 @@ class NodeCurl
 	static v8::Handle<v8::Value> perform(const v8::Arguments & args)
 	{
 		NodeCurl *curl = unwrap(args.This());
-
-		if (!curl->refer.IsEmpty())
-			return raise("The curl session is running, use curl.create() to create another session.");
-
-		curl->refer = v8::Persistent<v8::Object>::New(args.This());
-
 		CURLMcode code = curl_multi_add_handle(curlm, curl->curl);
 		if (code != CURLM_OK)
 		{