diff --git a/qutebrowser/browser/commands.py b/qutebrowser/browser/commands.py
index a0a550204..bab76668a 100644
--- a/qutebrowser/browser/commands.py
+++ b/qutebrowser/browser/commands.py
@@ -1210,19 +1210,21 @@ class CommandDispatcher:
         """Show the source of the current page."""
         # pylint: disable=no-member
         # WORKAROUND for https://bitbucket.org/logilab/pylint/issue/491/
-        widget = self._current_widget()
-        if widget.viewing_source:
+        tab = self._current_widget()
+        if tab.data.viewing_source:
             raise cmdexc.CommandError("Already viewing source!")
-        frame = widget.page().currentFrame()
-        html = frame.toHtml()
-        lexer = pygments.lexers.HtmlLexer()
-        formatter = pygments.formatters.HtmlFormatter(full=True,
-                                                      linenos='table')
-        highlighted = pygments.highlight(html, lexer, formatter)
-        current_url = self._current_url()
-        tab = self._tabbed_browser.tabopen(explicit=True)
-        tab.setHtml(highlighted, current_url)
-        tab.viewing_source = True
+
+        def show_source_cb(source):
+            lexer = pygments.lexers.HtmlLexer()
+            formatter = pygments.formatters.HtmlFormatter(full=True,
+                                                          linenos='table')
+            highlighted = pygments.highlight(source, lexer, formatter)
+            current_url = self._current_url()
+            new_tab = self._tabbed_browser.tabopen(explicit=True)
+            new_tab.set_html(highlighted, current_url)
+            new_tab.data.viewing_source = True
+
+        tab.dump_async(show_source_cb)
 
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        debug=True)
diff --git a/qutebrowser/browser/tab.py b/qutebrowser/browser/tab.py
index e1e6b3092..ce06cd7b9 100644
--- a/qutebrowser/browser/tab.py
+++ b/qutebrowser/browser/tab.py
@@ -73,7 +73,10 @@ class TabData(QObject):
     """
 
     def __init__(self):
-        self._data = {'keep_icon': False}
+        self._data = {
+            'keep_icon': False,
+            'viewing_source': False,
+        }
 
     def __getattr__(self, attr):
         if attr.startswith('_'):
@@ -459,6 +462,11 @@ class AbstractTab(QWidget):
         widget.setParent(self)
         self.setFocusProxy(widget)
 
+    @pyqtSlot()
+    def _on_load_started(self):
+        self.data.viewing_source = False
+        self.load_started.emit()
+
     @property
     def cur_url(self):
         raise NotImplementedError
diff --git a/qutebrowser/browser/webengine/webenginetab.py b/qutebrowser/browser/webengine/webenginetab.py
index 5b36e91e2..cd11f78e5 100644
--- a/qutebrowser/browser/webengine/webenginetab.py
+++ b/qutebrowser/browser/webengine/webenginetab.py
@@ -172,7 +172,7 @@ class WebEngineViewTab(tab.AbstractTab):
         page.windowCloseRequested.connect(self.window_close_requested)
         page.linkHovered.connect(self.link_hovered)
         page.loadProgress.connect(self.load_progress)
-        page.loadStarted.connect(self.load_started)
+        page.loadStarted.connect(self._on_load_started)
         view.titleChanged.connect(self.title_changed)
         page.loadFinished.connect(self.load_finished)
         # FIXME:refactor
diff --git a/qutebrowser/browser/webkit/webkittab.py b/qutebrowser/browser/webkit/webkittab.py
index 255ab7b63..6575e4c08 100644
--- a/qutebrowser/browser/webkit/webkittab.py
+++ b/qutebrowser/browser/webkit/webkittab.py
@@ -512,7 +512,7 @@ class WebViewTab(tab.AbstractTab):
         page.windowCloseRequested.connect(self.window_close_requested)
         page.linkHovered.connect(self.link_hovered)
         page.loadProgress.connect(self.load_progress)
-        frame.loadStarted.connect(self.load_started)
+        frame.loadStarted.connect(self._on_load_started)
         view.scroll_pos_changed.connect(self.scroll.perc_changed)
         view.titleChanged.connect(self.title_changed)
         view.url_text_changed.connect(self.url_text_changed)
diff --git a/qutebrowser/browser/webkit/webview.py b/qutebrowser/browser/webkit/webview.py
index f5450cbee..90b544053 100644
--- a/qutebrowser/browser/webkit/webview.py
+++ b/qutebrowser/browser/webkit/webview.py
@@ -50,8 +50,6 @@ class WebView(QWebView):
         statusbar_message: The current javascript statusbar message.
         inspector: The QWebInspector used for this webview.
         load_status: loading status of this page (index into LoadStatus)
-        viewing_source: Whether the webview is currently displaying source
-                        code.
         registry: The ObjectRegistry associated with this tab.
         win_id: The window ID of the view.
         _tab_id: The tab ID of the view.
@@ -118,7 +116,6 @@ class WebView(QWebView):
                                   window=win_id)
         mode_manager.entered.connect(self.on_mode_entered)
         mode_manager.left.connect(self.on_mode_left)
-        self.viewing_source = False
         if config.get('input', 'rocker-gestures'):
             self.setContextMenuPolicy(Qt.PreventContextMenu)
         self.urlChanged.connect(self.on_url_changed)
@@ -370,7 +367,6 @@ class WebView(QWebView):
     def on_load_started(self):
         """Leave insert/hint mode and set vars when a new page is loading."""
         self.progress = 0
-        self.viewing_source = False
         self._has_ssl_errors = False
         self._set_load_status(usertypes.LoadStatus.loading)