diff --git a/src/lib/app/mainapplication.cpp b/src/lib/app/mainapplication.cpp
index 4f8232dff..3e5079c11 100644
--- a/src/lib/app/mainapplication.cpp
+++ b/src/lib/app/mainapplication.cpp
@@ -103,6 +103,7 @@ MainApplication::MainApplication(int &argc, char** argv)
     , m_desktopNotifications(0)
     , m_webProfile(0)
     , m_autoSaver(0)
+    , m_newWindowId(0)
 #if defined(Q_OS_WIN) && !defined(Q_OS_OS2)
     , m_registerQAppAssociation(0)
 #endif
@@ -406,6 +407,11 @@ QList<BrowserWindow*> MainApplication::windows() const
     return m_windows;
 }
 
+QHash<BrowserWindow*, int> MainApplication::windowIdHash() const
+{
+    return m_windowIdHash;
+}
+
 BrowserWindow* MainApplication::getWindow() const
 {
     if (m_lastActiveWindow) {
@@ -425,6 +431,7 @@ BrowserWindow* MainApplication::createWindow(Qz::BrowserWindowType type, const Q
     connect(window, SIGNAL(destroyed(QObject*)), this, SLOT(windowDestroyed(QObject*)));
 
     m_windows.prepend(window);
+    m_windowIdHash.insert(window, m_newWindowId++);
     return window;
 }
 
@@ -868,6 +875,7 @@ void MainApplication::windowDestroyed(QObject* window)
     Q_ASSERT(m_windows.contains(static_cast<BrowserWindow*>(window)));
 
     m_windows.removeOne(static_cast<BrowserWindow*>(window));
+    m_windowIdHash.remove(static_cast<BrowserWindow*>(window));
 }
 
 void MainApplication::onFocusChanged()
diff --git a/src/lib/app/mainapplication.h b/src/lib/app/mainapplication.h
index b6dca475b..82d4ce434 100644
--- a/src/lib/app/mainapplication.h
+++ b/src/lib/app/mainapplication.h
@@ -76,6 +76,7 @@ public:
 
     int windowCount() const;
     QList<BrowserWindow*> windows() const;
+    QHash<BrowserWindow*, int> windowIdHash() const;
 
     BrowserWindow* getWindow() const;
     BrowserWindow* createWindow(Qz::BrowserWindowType type, const QUrl &startUrl = QUrl());
@@ -188,6 +189,8 @@ private:
     ProxyStyle *m_proxyStyle = nullptr;
 
     QList<BrowserWindow*> m_windows;
+    int m_newWindowId;
+    QHash<BrowserWindow*, int> m_windowIdHash;
     QPointer<BrowserWindow> m_lastActiveWindow;
 
     QList<PostLaunchAction> m_postLaunchActions;
diff --git a/src/lib/plugins/qml/api/tabs/qmltabs.cpp b/src/lib/plugins/qml/api/tabs/qmltabs.cpp
index b869d7b23..4db0b8b96 100644
--- a/src/lib/plugins/qml/api/tabs/qmltabs.cpp
+++ b/src/lib/plugins/qml/api/tabs/qmltabs.cpp
@@ -27,23 +27,6 @@ QmlTabs::QmlTabs(QObject *parent)
     }
 
     connect(mApp->plugins(), &PluginProxy::mainWindowCreated, this, &QmlTabs::windowCreated);
-
-    connect(mApp->plugins(), &PluginProxy::mainWindowDeleted, this, [this](BrowserWindow *window){
-        // FIXME: make it more efficient
-        windowIdHash.remove(window);
-        // If the window is not destroyed (which is almost always),
-        // then remove bias(= 1) from the index of window in the list
-        // for the correct index
-        int bias = 0;
-        for (int i = 0; i < mApp->windowCount(); i++) {
-            BrowserWindow *windowAtI = mApp->windows().at(i);
-            if (windowAtI == window) {
-                bias = 1;
-                continue;
-            }
-            windowIdHash[windowAtI] = i - bias;
-        }
-    });
 }
 
 bool QmlTabs::setCurrentIndex(const QVariantMap &map)
@@ -326,54 +309,46 @@ BrowserWindow *QmlTabs::getWindow(const QVariantMap &map) const
 {
     int windowId = map.value(QSL("windowId"), -1).toInt();
 
-    if (windowId < -1 || windowId >= mApp->windowCount()) {
-        qWarning() << "Unable to get window" << "windowId is out of bounds";
-        return nullptr;
-    }
-
-    BrowserWindow *window;
     if (windowId == -1) {
-        window = mApp->getWindow();
-    } else {
-        window = mApp->windows().at(windowId);
+        return mApp->getWindow();
     }
 
-    return window;
+    for(BrowserWindow *window : mApp->windowIdHash().keys()) {
+        if (mApp->windowIdHash().value(window) == windowId) {
+            return window;
+        }
+    }
+
+    qWarning() << "Unable to get window with given windowId";
+    return nullptr;
 }
 
 void QmlTabs::windowCreated(BrowserWindow *window)
 {
-    // FIXME: make it more efficient
-    for (int i = 0; i < mApp->windowCount(); i++) {
-        windowIdHash[mApp->windows().at(i)] = i;
-    }
+    int windowId = mApp->windowIdHash().value(window);
 
-    connect(window->tabWidget(), &TabWidget::changed, this, [this, window]{
+    connect(window->tabWidget(), &TabWidget::changed, this, [this, windowId]{
         QVariantMap map;
-        int windowId = windowIdHash.value(window);
         map.insert(QSL("windowId"), windowId);
         emit changed(map);
     });
 
-    connect(window->tabWidget(), &TabWidget::tabInserted, this, [this, window](int index){
+    connect(window->tabWidget(), &TabWidget::tabInserted, this, [this, windowId](int index){
         QVariantMap map;
-        int windowId = windowIdHash.value(window);
         map.insert(QSL("windowId"), windowId);
         map.insert(QSL("index"), index);
         emit tabInserted(map);
     });
 
-    connect(window->tabWidget(), &TabWidget::tabRemoved, this, [this, window](int index){
+    connect(window->tabWidget(), &TabWidget::tabRemoved, this, [this, windowId](int index){
         QVariantMap map;
-        int windowId = windowIdHash.value(window);
         map.insert(QSL("windowId"), windowId);
         map.insert(QSL("index"), index);
         emit tabRemoved(map);
     });
 
-    connect(window->tabWidget(), &TabWidget::tabMoved, this, [this, window](int from, int to){
+    connect(window->tabWidget(), &TabWidget::tabMoved, this, [this, windowId](int from, int to){
         QVariantMap map;
-        int windowId = windowIdHash.value(window);
         map.insert(QSL("windowId"), windowId);
         map.insert(QSL("from"), from);
         map.insert(QSL("to"), to);
diff --git a/src/lib/plugins/qml/api/tabs/qmltabs.h b/src/lib/plugins/qml/api/tabs/qmltabs.h
index f189c2dc1..33ae13de7 100644
--- a/src/lib/plugins/qml/api/tabs/qmltabs.h
+++ b/src/lib/plugins/qml/api/tabs/qmltabs.h
@@ -51,5 +51,4 @@ Q_SIGNALS:
 private:
     BrowserWindow *getWindow(const QVariantMap &map) const;
     void windowCreated(BrowserWindow *window);
-    QHash<BrowserWindow*, int> windowIdHash;
 };