diff --git a/meson.build b/meson.build
index d0ac9540..d649a6e1 100644
--- a/meson.build
+++ b/meson.build
@@ -50,7 +50,7 @@ valac = meson.get_compiler('vala')
 # Required libraries and other dependencies
 #
 
-target_vala = '0.46.2'
+target_vala = '0.48.6'
 target_glib = '2.60.4'
 target_gtk = '3.24.7'
 target_webkit = '2.26'
diff --git a/src/client/accounts/accounts-manager.vala b/src/client/accounts/accounts-manager.vala
index c0ead2bb..f9c2bdff 100644
--- a/src/client/accounts/accounts-manager.vala
+++ b/src/client/accounts/accounts-manager.vala
@@ -306,7 +306,7 @@ public class Accounts.Manager : GLib.Object {
      * restore_account}.
      */
     public async void remove_account(Geary.AccountInformation account,
-                                     GLib.Cancellable cancellable)
+                                     GLib.Cancellable? cancellable)
         throws GLib.Error {
         this.accounts.unset(account.id);
         this.removed.add(account);
@@ -324,7 +324,7 @@ public class Accounts.Manager : GLib.Object {
      * he account was removed.
      */
     public async void restore_account(Geary.AccountInformation account,
-                                      GLib.Cancellable cancellable)
+                                      GLib.Cancellable? cancellable)
         throws GLib.Error {
         if (this.removed.remove(account)) {
             yield save_account(account, cancellable);
diff --git a/src/client/application/application-client.vala b/src/client/application/application-client.vala
index 43002728..3585a5a4 100644
--- a/src/client/application/application-client.vala
+++ b/src/client/application/application-client.vala
@@ -1184,11 +1184,14 @@ public class Application.Client : Gtk.Application {
     private void on_activate_new_window() {
         // If there was an existing active main, select the same
         // account/folder/conversation.
+        Geary.Folder? folder = null;
+        Gee.Collection<Geary.App.Conversation>? conversations = null;
         MainWindow? current = this.last_active_main_window;
-        this.new_window.begin(
-            current.selected_folder,
-            current.conversation_list_view.copy_selected()
-        );
+        if (current != null) {
+            folder = current.selected_folder;
+            conversations = current.conversation_list_view.copy_selected();
+        }
+        this.new_window.begin(folder, conversations);
     }
 
     private void on_activate_preferences() {
diff --git a/src/client/application/application-controller.vala b/src/client/application/application-controller.vala
index 38b1bfea..234c7485 100644
--- a/src/client/application/application-controller.vala
+++ b/src/client/application/application-controller.vala
@@ -947,6 +947,16 @@ internal class Application.Controller :
         }
     }
 
+    private void add_account(Geary.AccountInformation added) {
+        try {
+            this.application.engine.add_account(added);
+        } catch (Geary.EngineError.ALREADY_EXISTS err) {
+            // all good
+        } catch (GLib.Error err) {
+            report_problem(new Geary.AccountProblemReport(added, err));
+        }
+    }
+
     private async void open_account(Geary.Account account) {
         AccountContext context = new AccountContext(
             account,
@@ -1012,6 +1022,19 @@ internal class Application.Controller :
         update_account_status();
     }
 
+    private async void remove_account(Geary.AccountInformation removed) {
+        yield close_account(removed, false);
+        try {
+            this.application.engine.remove_account(removed);
+        } catch (Geary.EngineError.NOT_FOUND err) {
+            // all good
+        } catch (GLib.Error err) {
+            report_problem(
+                new Geary.AccountProblemReport(removed, err)
+            );
+        }
+    }
+
     private async void close_account(Geary.AccountInformation config,
                                      bool is_shutdown) {
         AccountContext? context = this.accounts.get(config);
@@ -1540,11 +1563,7 @@ internal class Application.Controller :
     private void on_account_added(Geary.AccountInformation added,
                                   Accounts.Manager.Status status) {
         if (status == Accounts.Manager.Status.ENABLED) {
-            try {
-                this.application.engine.add_account(added);
-            } catch (GLib.Error err) {
-                report_problem(new Geary.AccountProblemReport(added, err));
-            }
+            this.add_account(added);
         }
     }
 
@@ -1552,33 +1571,12 @@ internal class Application.Controller :
                                            Accounts.Manager.Status status) {
         switch (status) {
         case Accounts.Manager.Status.ENABLED:
-            if (!this.application.engine.has_account(changed)) {
-                try {
-                    this.application.engine.add_account(changed);
-                } catch (GLib.Error err) {
-                    report_problem(new Geary.AccountProblemReport(changed, err));
-                }
-            }
+            this.add_account(changed);
             break;
 
         case Accounts.Manager.Status.UNAVAILABLE:
         case Accounts.Manager.Status.DISABLED:
-            if (this.application.engine.has_account(changed)) {
-                this.close_account.begin(
-                    changed,
-                    false,
-                    (obj, res) => {
-                        this.close_account.end(res);
-                        try {
-                            this.application.engine.remove_account(changed);
-                        } catch (GLib.Error err) {
-                            report_problem(
-                                new Geary.AccountProblemReport(changed, err)
-                            );
-                        }
-                    }
-                );
-            }
+            this.remove_account.begin(changed);
             break;
 
         case Accounts.Manager.Status.REMOVED:
@@ -1588,23 +1586,7 @@ internal class Application.Controller :
     }
 
     private void on_account_removed(Geary.AccountInformation removed) {
-        debug("%s: Closing account for removal", removed.id);
-        this.close_account.begin(
-            removed,
-            false,
-            (obj, res) => {
-                this.close_account.end(res);
-                debug("%s: Account closed", removed.id);
-                try {
-                    this.application.engine.remove_account(removed);
-                    debug("%s: Account removed from engine", removed.id);
-                } catch (GLib.Error err) {
-                    report_problem(
-                        new Geary.AccountProblemReport(removed, err)
-                    );
-                }
-            }
-        );
+        this.remove_account.begin(removed);
     }
 
     private void on_report_problem(Geary.ProblemReport problem) {