diff --git a/qutebrowser/config/configfiles.py b/qutebrowser/config/configfiles.py
index e19e15695..2220de93d 100644
--- a/qutebrowser/config/configfiles.py
+++ b/qutebrowser/config/configfiles.py
@@ -175,10 +175,10 @@ class YamlConfig(QObject):
                 new_name = configdata.MIGRATIONS.renamed[name]
                 log.config.debug("Renaming {} to {}".format(name, new_name))
                 self._values[new_name] = self._values[name]
-                del self._values[name]
+                self.unset(name)
             elif name in configdata.MIGRATIONS.deleted:
                 log.config.debug("Removing {}".format(name))
-                del self._values[name]
+                self.unset(name)
         persist = 'tabs.persist_mode_on_change'
         if persist in self._values:
             if self._values[persist]:
diff --git a/tests/unit/config/test_configfiles.py b/tests/unit/config/test_configfiles.py
index 101b883cd..341fad689 100644
--- a/tests/unit/config/test_configfiles.py
+++ b/tests/unit/config/test_configfiles.py
@@ -152,7 +152,7 @@ class TestYaml:
         yaml._save()
 
         lines = autoconfig.read_text('utf-8').splitlines()
-        assert '  hello:' not in lines
+        assert '  hello: world' not in lines
 
     def test_renamed_key(self, monkeypatch, yaml, config_tmpdir):
         """A key marked as renamed should be renamed properly."""
@@ -166,34 +166,22 @@ class TestYaml:
         yaml._save()
 
         lines = autoconfig.read_text('utf-8').splitlines()
-        assert '  old:' not in lines
-        assert '  new:' not in lines
+        assert '  old: value' not in lines
+        assert '  tabs.show: value' in lines
 
-    def test_merge_persist_false(self, monkeypatch, yaml, config_tmpdir):
-        """Migration of tabs.persist_mode_on_change: False."""
+    @pytest.mark.parametrize('persist', [True, False])
+    def test_merge_persist(self, yaml, config_tmpdir, persist):
+        """Tests for migration of tabs.persist_mode_on_change."""
         autoconfig = config_tmpdir / 'autoconfig.yml'
-        autoconfig.write_text('global:\n  tabs.persist_mode_on_change: False',
-                              encoding='utf-8')
-
+        autoconfig.write_text('global:\n  tabs.persist_mode_on_change: {}'.
+                              format(persist), encoding='utf-8')
         yaml.load()
         yaml._save()
 
         lines = autoconfig.read_text('utf-8').splitlines()
+        mode = 'persist' if persist else 'normal'
         assert '  tabs.persist_mode_on_change:' not in lines
-        assert '  tabs.mode_on_change: normal' in lines
-
-    def test_merge_persist_true(self, monkeypatch, yaml, config_tmpdir):
-        """Migration of tabs.persist_mode_on_change: True."""
-        autoconfig = config_tmpdir / 'autoconfig.yml'
-        autoconfig.write_text('global:\n  tabs.persist_mode_on_change: True',
-                              encoding='utf-8')
-
-        yaml.load()
-        yaml._save()
-
-        lines = autoconfig.read_text('utf-8').splitlines()
-        assert '  tabs.persist_mode_on_change:' not in lines
-        assert '  tabs.mode_on_change: persist' in lines
+        assert '  tabs.mode_on_change: {}'.format(mode) in lines
 
     def test_renamed_key_unknown_target(self, monkeypatch, yaml,
                                         config_tmpdir):