diff --git a/qutebrowser/completion/models/completionmodel.py b/qutebrowser/completion/models/completionmodel.py
index 778e0cac9..3e48076e5 100644
--- a/qutebrowser/completion/models/completionmodel.py
+++ b/qutebrowser/completion/models/completionmodel.py
@@ -59,6 +59,7 @@ class CompletionModel(QAbstractItemModel):
     def add_category(self, cat):
         """Add a completion category to the model."""
         self._categories.append(cat)
+        cat.layoutAboutToBeChanged.connect(self.layoutAboutToBeChanged)
         cat.layoutChanged.connect(self.layoutChanged)
 
     def data(self, index, role=Qt.DisplayRole):
diff --git a/qutebrowser/completion/models/sqlcategory.py b/qutebrowser/completion/models/sqlcategory.py
index 4819e940b..2664edbfe 100644
--- a/qutebrowser/completion/models/sqlcategory.py
+++ b/qutebrowser/completion/models/sqlcategory.py
@@ -59,6 +59,8 @@ class SqlCategory(QSqlQueryModel):
         if sort_by:
             assert sort_order in ['asc', 'desc'], sort_order
             querystr += ' order by {} {}'.format(sort_by, sort_order)
+        else:
+            assert sort_order is None, sort_order
 
         self._query = sql.Query(querystr, forward_only=False)
 
diff --git a/qutebrowser/misc/sql.py b/qutebrowser/misc/sql.py
index 4ae37f01f..a288df475 100644
--- a/qutebrowser/misc/sql.py
+++ b/qutebrowser/misc/sql.py
@@ -38,7 +38,8 @@ def init(db_path):
     """Initialize the SQL database connection."""
     database = QSqlDatabase.addDatabase('QSQLITE')
     if not database.isValid():
-        raise SqlException('Failed to add database. Is sqlite installed?')
+        raise SqlException('Failed to add database. '
+            'Are sqlite and Qt sqlite support installed?')
     database.setDatabaseName(db_path)
     if not database.open():
         raise SqlException("Failed to open sqlite database at {}: {}"
diff --git a/tests/unit/completion/test_completionmodel.py b/tests/unit/completion/test_completionmodel.py
index ce0fe3765..4d1d3f123 100644
--- a/tests/unit/completion/test_completionmodel.py
+++ b/tests/unit/completion/test_completionmodel.py
@@ -36,7 +36,7 @@ def test_first_last_item(counts):
     """Test that first() and last() index to the first and last items."""
     model = completionmodel.CompletionModel()
     for c in counts:
-        cat = mock.Mock(spec=['layoutChanged'])
+        cat = mock.Mock(spec=['layoutChanged', 'layoutAboutToBeChanged'])
         cat.rowCount = mock.Mock(return_value=c, spec=[])
         model.add_category(cat)
     data = [i for i, rowCount in enumerate(counts) if rowCount > 0]
@@ -60,7 +60,8 @@ def test_first_last_item(counts):
 def test_count(counts):
     model = completionmodel.CompletionModel()
     for c in counts:
-        cat = mock.Mock(spec=['rowCount', 'layoutChanged'])
+        cat = mock.Mock(spec=['rowCount', 'layoutChanged',
+                              'layoutAboutToBeChanged'])
         cat.rowCount = mock.Mock(return_value=c, spec=[])
         model.add_category(cat)
     assert model.count() == sum(counts)
@@ -70,7 +71,9 @@ 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', 'layoutChanged']) for _ in range(3)]
+    cats = [mock.Mock(spec=['set_pattern', 'layoutChanged',
+                            'layoutAboutToBeChanged'])
+            for _ in range(3)]
     for c in cats:
         c.set_pattern = mock.Mock(spec=[])
         model.add_category(c)
diff --git a/tests/unit/completion/test_sqlcategory.py b/tests/unit/completion/test_sqlcategory.py
index 851bad257..a9321e33e 100644
--- a/tests/unit/completion/test_sqlcategory.py
+++ b/tests/unit/completion/test_sqlcategory.py
@@ -32,7 +32,7 @@ pytestmark = pytest.mark.usefixtures('init_sql')
 
 
 @pytest.mark.parametrize('sort_by, sort_order, data, expected', [
-    (None, 'asc',
+    (None, None,
      [('B', 'C', 'D'), ('A', 'F', 'C'), ('C', 'A', 'G')],
      [('B', 'C', 'D'), ('A', 'F', 'C'), ('C', 'A', 'G')]),