diff --git a/src/MainWindow.vala b/src/MainWindow.vala
index 65cc3c208..23b1f0d16 100644
--- a/src/MainWindow.vala
+++ b/src/MainWindow.vala
@@ -38,7 +38,7 @@ public class Tasks.MainWindow : Hdy.ApplicationWindow {
     construct {
         add_action_entries (ACTION_ENTRIES, this);
 
-        var application_instance = (Gtk.Application) GLib.Application.get_default ();
+        unowned var application_instance = (Gtk.Application) GLib.Application.get_default ();
         foreach (var action in action_accelerators.get_keys ()) {
             application_instance.set_accels_for_action (
                 ACTION_PREFIX + action, action_accelerators[action].to_array ()
@@ -233,7 +233,7 @@ public class Tasks.MainWindow : Hdy.ApplicationWindow {
                 var task_lists = registry.list_sources (E.SOURCE_EXTENSION_TASK_LIST);
 
                 task_lists.foreach ((source) => {
-                    E.SourceTaskList list = (E.SourceTaskList)source.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
+                    unowned var list = (E.SourceTaskList)source.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
 
                     if (list.selected == true && source.enabled == true && !source.has_extension (E.SOURCE_EXTENSION_COLLECTION)) {
                         add_source (source);
@@ -256,7 +256,7 @@ public class Tasks.MainWindow : Hdy.ApplicationWindow {
 
         try {
             var new_source = new E.Source (null, null);
-            var new_source_tasklist_extension = (E.SourceTaskList) new_source.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
+            unowned var new_source_tasklist_extension = (E.SourceTaskList) new_source.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
             new_source.display_name = _("New list");
             new_source_tasklist_extension.color = "#0e9a83";
 
@@ -296,7 +296,7 @@ public class Tasks.MainWindow : Hdy.ApplicationWindow {
     }
 
     private void action_delete_selected_list () {
-        var list_row = ((Tasks.Widgets.SourceRow) listbox.get_selected_row ());
+        unowned var list_row = ((Tasks.Widgets.SourceRow) listbox.get_selected_row ());
         var source = list_row.source;
 
         if (Tasks.Application.model.is_remove_task_list_supported (source)) {
@@ -310,7 +310,7 @@ public class Tasks.MainWindow : Hdy.ApplicationWindow {
                 transient_for = this
             };
 
-            unowned Gtk.Widget trash_button = message_dialog.add_button (_("Delete Anyway"), Gtk.ResponseType.YES);
+            unowned var trash_button = message_dialog.add_button (_("Delete Anyway"), Gtk.ResponseType.YES);
             trash_button.get_style_context ().add_class (Gtk.STYLE_CLASS_DESTRUCTIVE_ACTION);
 
             message_dialog.response.connect ((response) => {
@@ -421,7 +421,7 @@ public class Tasks.MainWindow : Hdy.ApplicationWindow {
     }
 
     private void update_source (E.Source source) {
-        E.SourceTaskList list = (E.SourceTaskList)source.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
+        unowned var list = (E.SourceTaskList)source.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
 
         if (list.selected != true || source.enabled != true) {
             remove_source (source);
@@ -432,7 +432,7 @@ public class Tasks.MainWindow : Hdy.ApplicationWindow {
         } else {
             source_rows[source].update_request ();
 
-            var task_list_grid = (Tasks.Widgets.TaskListGrid) task_list_grid_stack.get_visible_child ();
+            unowned var task_list_grid = (Tasks.Widgets.TaskListGrid) task_list_grid_stack.get_visible_child ();
             if (task_list_grid != null) {
                 task_list_grid.update_request ();
             }
diff --git a/src/TaskModel.vala b/src/TaskModel.vala
index 0973e4c8a..f7aa339c3 100644
--- a/src/TaskModel.vala
+++ b/src/TaskModel.vala
@@ -260,7 +260,7 @@ public class Tasks.TaskModel : Object {
 
     public async void add_task_list (E.Source task_list, E.Source collection_or_sibling) throws Error {
         var registry = get_registry_sync ();
-        var task_list_extension = (E.SourceTaskList) task_list.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
+        unowned var task_list_extension = (E.SourceTaskList) task_list.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
         var backend_name = get_collection_backend_name (collection_or_sibling, registry);
 
         switch (backend_name.down ()) {
@@ -592,7 +592,7 @@ public class Tasks.TaskModel : Object {
             debug ("WebDAV Rename '%s'", task_list.get_uid ());
 
             var collection_source_webdav_session = new E.WebDAVSession (collection_source);
-            var source_webdav_extension = (E.SourceWebdav) task_list.get_extension (E.SOURCE_EXTENSION_WEBDAV_BACKEND);
+            unowned var source_webdav_extension = (E.SourceWebdav) task_list.get_extension (E.SOURCE_EXTENSION_WEBDAV_BACKEND);
 
             var credentials_provider = new E.SourceCredentialsProvider (registry);
             E.NamedParameters credentials;
@@ -676,7 +676,7 @@ public class Tasks.TaskModel : Object {
         if (!task_list.has_extension (E.SOURCE_EXTENSION_TASK_LIST)) {
             throw new Tasks.TaskModelError.INVALID_ARGUMENT ("Changing the color is not supported by this source.");
         }
-        var task_list_extension = (E.SourceTaskList) task_list.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
+        unowned var task_list_extension = (E.SourceTaskList) task_list.get_extension (E.SOURCE_EXTENSION_TASK_LIST);
         var previous_color = task_list_extension.dup_color ();
 
         var registry = get_registry_sync ();
@@ -700,7 +700,7 @@ public class Tasks.TaskModel : Object {
                     debug ("Update %s color for '%s'", backend_name, task_list.get_uid ());
 
                     var collection_source_webdav_session = new E.WebDAVSession (collection_source);
-                    var source_webdav_extension = (E.SourceWebdav) task_list.get_extension (E.SOURCE_EXTENSION_WEBDAV_BACKEND);
+                    unowned var source_webdav_extension = (E.SourceWebdav) task_list.get_extension (E.SOURCE_EXTENSION_WEBDAV_BACKEND);
 
                     var credentials_provider = new E.SourceCredentialsProvider (registry);
                     E.NamedParameters credentials;
@@ -750,7 +750,7 @@ public class Tasks.TaskModel : Object {
 
     public async void add_task (E.Source list, ECal.Component task) throws Error {
         ECal.Client client = get_client (list);
-        unowned ICal.Component comp = task.get_icalcomponent ();
+        unowned var comp = task.get_icalcomponent ();
 
         debug (@"Adding task '$(comp.get_uid())'");
 
@@ -764,7 +764,7 @@ public class Tasks.TaskModel : Object {
     public async void complete_task (E.Source list, ECal.Component task) throws Error {
         ECal.Client client = get_client (list);
 
-        unowned ICal.Component comp = task.get_icalcomponent ();
+        unowned var comp = task.get_icalcomponent ();
         var was_completed = comp.get_status () == ICal.PropertyStatus.COMPLETED;
 
         if (was_completed) {
@@ -831,7 +831,7 @@ public class Tasks.TaskModel : Object {
 
     public async void update_task (E.Source list, ECal.Component task, ECal.ObjModType mod_type) throws Error {
         ECal.Client client = get_client (list);
-        unowned ICal.Component comp = task.get_icalcomponent ();
+        unowned var comp = task.get_icalcomponent ();
 
         debug (@"Updating task '$(comp.get_uid())' [mod_type=$(mod_type)]");
         yield client.modify_object (comp, mod_type, ECal.OperationFlags.NONE, null);
@@ -839,7 +839,7 @@ public class Tasks.TaskModel : Object {
 
     public async void remove_task (E.Source list, ECal.Component task, ECal.ObjModType mod_type) throws Error {
         ECal.Client client = get_client (list);
-        unowned ICal.Component comp = task.get_icalcomponent ();
+        unowned var comp = task.get_icalcomponent ();
 
         string uid = comp.get_uid ();
         string? rid = task.has_recurrences () ? null : task.get_recurid_as_string ();
@@ -881,7 +881,7 @@ public class Tasks.TaskModel : Object {
     }
 
     private void debug_task (E.Source task_list, ECal.Component task) {
-        unowned ICal.Component comp = task.get_icalcomponent ();
+        unowned var comp = task.get_icalcomponent ();
         var task_summary = comp.get_summary ();
         var task_uid = comp.get_uid ();
         var task_list_display_name = task_list.dup_display_name ();
diff --git a/src/Widgets/TaskListGrid.vala b/src/Widgets/TaskListGrid.vala
index 7ad64c84c..f02d11c98 100644
--- a/src/Widgets/TaskListGrid.vala
+++ b/src/Widgets/TaskListGrid.vala
@@ -360,7 +360,7 @@ public class Tasks.Widgets.TaskListGrid : Gtk.Grid {
     }
 
     private void on_tasks_modified (Gee.Collection<ECal.Component> tasks) {
-        Tasks.Widgets.TaskRow task_row = null;
+        unowned Tasks.Widgets.TaskRow task_row = null;
         var row_index = 0;
 
         do {