diff --git a/qutebrowser/app.py b/qutebrowser/app.py
index c9b521f50..1cfdbc876 100644
--- a/qutebrowser/app.py
+++ b/qutebrowser/app.py
@@ -372,7 +372,7 @@ class Application(QApplication):
         # syntactic sugar
         kp = self._keyparsers
         status = self.mainwindow.status
-        completion = self.mainwindow.completion
+        completion = self.registry['completion']
         tabs = self.mainwindow.tabs
         cmd = self.registry['status-cmd']
         completer = self.registry['completer']
diff --git a/qutebrowser/widgets/completion.py b/qutebrowser/widgets/completion.py
index 12e2dc6b5..68da7576a 100644
--- a/qutebrowser/widgets/completion.py
+++ b/qutebrowser/widgets/completion.py
@@ -210,13 +210,13 @@ class CompletionView(QTreeView):
             selmod.clearSelection()
             selmod.clearCurrentIndex()
 
-    @cmdutils.register(instance='mainwindow.completion', hide=True,
+    @cmdutils.register(instance='completion', hide=True,
                        modes=[usertypes.KeyMode.command])
     def completion_item_prev(self):
         """Select the previous completion item."""
         self._next_prev_item(prev=True)
 
-    @cmdutils.register(instance='mainwindow.completion', hide=True,
+    @cmdutils.register(instance='completion', hide=True,
                        modes=[usertypes.KeyMode.command])
     def completion_item_next(self):
         """Select the next completion item."""
diff --git a/qutebrowser/widgets/mainwindow.py b/qutebrowser/widgets/mainwindow.py
index cf41e21fc..ab7bb7917 100644
--- a/qutebrowser/widgets/mainwindow.py
+++ b/qutebrowser/widgets/mainwindow.py
@@ -85,7 +85,8 @@ class MainWindow(QWidget):
         self.tabs.title_changed.connect(self.setWindowTitle)
         self._vbox.addWidget(self.tabs)
 
-        self.completion = completion.CompletionView(self)
+        self._completion = completion.CompletionView(self)
+        utils.register_object('completion', self._completion)
 
         self.status = bar.StatusBar()
         self._vbox.addWidget(self.status)
@@ -93,7 +94,8 @@ class MainWindow(QWidget):
         # When we're here the statusbar might not even really exist yet, so
         # resizing will fail. Therefore, we use singleShot QTimers to make sure
         # we defer this until everything else is initialized.
-        QTimer.singleShot(0, lambda: self.completion.resize_completion.connect(
+        QTimer.singleShot(
+            0, lambda: self._completion.resize_completion.connect(
             self.resize_completion))
         QTimer.singleShot(0, self.resize_completion)
         #self.retranslateUi(MainWindow)
@@ -126,8 +128,8 @@ class MainWindow(QWidget):
         # Shrink to content size if needed and shrinking is enabled
         if config.get('completion', 'shrink'):
             contents_height = (
-                self.completion.viewportSizeHint().height() +
-                self.completion.horizontalScrollBar().sizeHint().height())
+                self._completion.viewportSizeHint().height() +
+                self._completion.horizontalScrollBar().sizeHint().height())
             if contents_height <= height:
                 height = contents_height
         else:
@@ -140,7 +142,7 @@ class MainWindow(QWidget):
         bottomright = self.status.geometry().topRight()
         rect = QRect(topleft, bottomright)
         if rect.isValid():
-            self.completion.setGeometry(rect)
+            self._completion.setGeometry(rect)
 
     @cmdutils.register(instance='mainwindow', name=['quit', 'q'])
     def close(self):