diff --git a/qutebrowser/completion/completer.py b/qutebrowser/completion/completer.py
index ae2e9e4bb..491fe2e04 100644
--- a/qutebrowser/completion/completer.py
+++ b/qutebrowser/completion/completer.py
@@ -224,20 +224,19 @@ class Completer(QObject):
         if func is None:
             log.completion.debug('Clearing completion')
             completion.set_model(None)
-        elif func != self._last_completion_func:
+            self._last_completion_func = None
+            return
+
+        if func != self._last_completion_func:
             self._last_completion_func = func
             args = (x for x in before_cursor[1:] if not x.startswith('-'))
             with debug.log_time(log.completion,
-                    'Instantiate {} completion'.format(func.__name__)):
+                    'Starting {} completion'.format(func.__name__)):
                 model = func(*args)
             with debug.log_time(log.completion, 'Set completion model'):
                 completion.set_model(model)
-            completion.set_pattern(pattern)
-        else:
-            log.completion.debug('Setting pattern {}'.format(pattern))
-            completion.set_pattern(pattern)
 
-        self._last_completion_func = None
+        completion.set_pattern(pattern)
 
     def _change_completed_part(self, newtext, before, after, immediate=False):
         """Change the part we're currently completing in the commandline.
diff --git a/qutebrowser/completion/completionwidget.py b/qutebrowser/completion/completionwidget.py
index 1f8b3d9f4..711301b4c 100644
--- a/qutebrowser/completion/completionwidget.py
+++ b/qutebrowser/completion/completionwidget.py
@@ -283,8 +283,6 @@ class CompletionView(QTreeView):
         self._column_widths = model.column_widths
         self._active = True
 
-        self.set_pattern('')
-
         if (config.get('completion', 'show') == 'always' and
                 model.count() > 0):
             self.show()
diff --git a/qutebrowser/completion/models/completionmodel.py b/qutebrowser/completion/models/completionmodel.py
index 9543792ed..cbc20470c 100644
--- a/qutebrowser/completion/models/completionmodel.py
+++ b/qutebrowser/completion/models/completionmodel.py
@@ -63,6 +63,7 @@ class CompletionModel(QAbstractItemModel):
     def add_category(self, cat):
         """Add a completion category to the model."""
         self._categories.append(cat)
+        cat.layoutChanged.connect(self.layoutChanged)
 
     def data(self, index, role=Qt.DisplayRole):
         """Return the item data for index.
diff --git a/tests/unit/completion/test_completionmodel.py b/tests/unit/completion/test_completionmodel.py
index 8d43f2883..8f8acced2 100644
--- a/tests/unit/completion/test_completionmodel.py
+++ b/tests/unit/completion/test_completionmodel.py
@@ -56,7 +56,7 @@ def test_first_last_item(counts):
 def test_count(counts):
     model = completionmodel.CompletionModel()
     for c in counts:
-        cat = mock.Mock(spec=['rowCount'])
+        cat = mock.Mock(spec=['rowCount', 'layoutChanged'])
         cat.rowCount = mock.Mock(return_value=c)
         model.add_category(cat)
     assert model.count() == sum(counts)
@@ -66,7 +66,7 @@ def test_count(counts):
 def test_set_pattern(pat):
     """Validate the filtering and sorting results of set_pattern."""
     model = completionmodel.CompletionModel()
-    cats = [mock.Mock(spec=['set_pattern'])] * 3
+    cats = [mock.Mock(spec=['set_pattern', 'layoutChanged'])] * 3
     for c in cats:
         c.set_pattern = mock.Mock()
         model.add_category(c)