diff --git a/src/qpython.cpp b/src/qpython.cpp
index 236cfff..d9ea810 100644
--- a/src/qpython.cpp
+++ b/src/qpython.cpp
@@ -45,15 +45,15 @@ QPython::QPython(QObject *parent)
     QObject::connect(priv, SIGNAL(receive(QVariant)),
                      this, SLOT(receive(QVariant)));
 
-    QObject::connect(this, SIGNAL(process(QString,QVariant,QJSValue)),
-                     worker, SLOT(process(QString,QVariant,QJSValue)));
-    QObject::connect(worker, SIGNAL(finished(QVariant,QJSValue)),
-                     this, SLOT(finished(QVariant,QJSValue)));
+    QObject::connect(this, SIGNAL(process(QString,QVariant,QJSValue *)),
+                     worker, SLOT(process(QString,QVariant,QJSValue *)));
+    QObject::connect(worker, SIGNAL(finished(QVariant,QJSValue *)),
+                     this, SLOT(finished(QVariant,QJSValue *)));
 
-    QObject::connect(this, SIGNAL(import(QString,QJSValue)),
-                     worker, SLOT(import(QString,QJSValue)));
-    QObject::connect(worker, SIGNAL(imported(bool,QJSValue)),
-                     this, SLOT(imported(bool,QJSValue)));
+    QObject::connect(this, SIGNAL(import(QString,QJSValue *)),
+                     worker, SLOT(import(QString,QJSValue *)));
+    QObject::connect(worker, SIGNAL(imported(bool,QJSValue *)),
+                     this, SLOT(imported(bool,QJSValue *)));
 
     thread.setObjectName("QPythonWorker");
     thread.start();
@@ -84,7 +84,11 @@ QPython::addImportPath(QString path)
 void
 QPython::importModule(QString name, QJSValue callback)
 {
-    emit import(name, callback);
+    QJSValue *cb = 0;
+    if (!callback.isNull() && !callback.isUndefined() && callback.isCallable()) {
+        cb = new QJSValue(callback);
+    }
+    emit import(name, cb);
 }
 
 bool
@@ -168,7 +172,11 @@ QPython::evaluate(QString expr)
 void
 QPython::call(QString func, QVariant args, QJSValue callback)
 {
-    emit process(func, args, callback);
+    QJSValue *cb = 0;
+    if (!callback.isNull() && !callback.isUndefined() && callback.isCallable()) {
+        cb = new QJSValue(callback);
+    }
+    emit process(func, args, cb);
 }
 
 QVariant
@@ -220,23 +228,21 @@ QPython::call_sync(QString func, QVariant args)
 }
 
 void
-QPython::finished(QVariant result, QJSValue callback)
+QPython::finished(QVariant result, QJSValue *callback)
 {
-    if (!callback.isNull() && !callback.isUndefined() && callback.isCallable()) {
-        QJSValueList args;
-        QJSValue v = callback.engine()->toScriptValue(result);
-        args << v;
-        callback.call(args);
-    }
+    QJSValueList args;
+    QJSValue v = callback->engine()->toScriptValue(result);
+    args << v;
+    callback->call(args);
+    delete callback;
 }
 
 void
-QPython::imported(bool result, QJSValue callback)
+QPython::imported(bool result, QJSValue *callback)
 {
-    if (!callback.isNull() && !callback.isUndefined() && callback.isCallable()) {
-        QJSValueList args;
-        QJSValue v = callback.engine()->toScriptValue(QVariant(result));
-        args << v;
-        callback.call(args);
-    }
+    QJSValueList args;
+    QJSValue v = callback->engine()->toScriptValue(QVariant(result));
+    args << v;
+    callback->call(args);
+    delete callback;
 }
diff --git a/src/qpython.h b/src/qpython.h
index aba8af7..f05a4b6 100644
--- a/src/qpython.h
+++ b/src/qpython.h
@@ -260,14 +260,14 @@ class QPython : public QObject {
         void error(QString traceback);
 
         /* For internal use only */
-        void process(QString func, QVariant args, QJSValue callback);
-        void import(QString name, QJSValue callback);
+        void process(QString func, QVariant args, QJSValue *callback);
+        void import(QString name, QJSValue *callback);
 
     private slots:
         void receive(QVariant data);
 
-        void finished(QVariant result, QJSValue callback);
-        void imported(bool result, QJSValue callback);
+        void finished(QVariant result, QJSValue *callback);
+        void imported(bool result, QJSValue *callback);
 
     private:
         static QPythonPriv *priv;
diff --git a/src/qpython_worker.cpp b/src/qpython_worker.cpp
index cce3322..dab6a84 100644
--- a/src/qpython_worker.cpp
+++ b/src/qpython_worker.cpp
@@ -32,15 +32,19 @@ QPythonWorker::~QPythonWorker()
 }
 
 void
-QPythonWorker::process(QString func, QVariant args, QJSValue callback)
+QPythonWorker::process(QString func, QVariant args, QJSValue *callback)
 {
     QVariant result = qpython->call_sync(func, args);
-    emit finished(result, callback);
+    if (callback) {
+        emit finished(result, callback);
+    }
 }
 
 void
-QPythonWorker::import(QString name, QJSValue callback)
+QPythonWorker::import(QString name, QJSValue *callback)
 {
     bool result = qpython->importModule_sync(name);
-    emit imported(result, callback);
+    if (callback) {
+        emit imported(result, callback);
+    }
 }
diff --git a/src/qpython_worker.h b/src/qpython_worker.h
index 3fce88c..a8076b8 100644
--- a/src/qpython_worker.h
+++ b/src/qpython_worker.h
@@ -34,12 +34,12 @@ class QPythonWorker : public QObject {
         ~QPythonWorker();
 
     public slots:
-        void process(QString func, QVariant args, QJSValue callback);
-        void import(QString func, QJSValue callback);
+        void process(QString func, QVariant args, QJSValue *callback);
+        void import(QString func, QJSValue *callback);
 
     signals:
-        void finished(QVariant result, QJSValue callback);
-        void imported(bool result, QJSValue callback);
+        void finished(QVariant result, QJSValue *callback);
+        void imported(bool result, QJSValue *callback);
 
     private:
         QPython *qpython;