diff --git a/src/engine/imap/command/imap-command.vala b/src/engine/imap/command/imap-command.vala
index 570fe3ba..58163671 100644
--- a/src/engine/imap/command/imap-command.vala
+++ b/src/engine/imap/command/imap-command.vala
@@ -17,7 +17,7 @@
  *
  * See [[http://tools.ietf.org/html/rfc3501#section-6]]
  */
-public class Geary.Imap.Command : BaseObject {
+public abstract class Geary.Imap.Command : BaseObject {
 
     /**
      * Default timeout to wait for a server response for a command.
@@ -97,7 +97,7 @@ public class Geary.Imap.Command : BaseObject {
      *
      * @see Tag
      */
-    public Command(string name, string[]? args = null) {
+    protected Command(string name, string[]? args = null) {
         this.tag = Tag.get_unassigned();
         this.name = name;
         if (args != null) {
@@ -250,7 +250,7 @@ public class Geary.Imap.Command : BaseObject {
      * cancelled, if the command timed out, or if the command's
      * response was bad.
      */
-    public async void wait_until_complete(GLib.Cancellable cancellable)
+    public async void wait_until_complete(GLib.Cancellable? cancellable)
         throws GLib.Error {
         yield this.complete_lock.wait_async(cancellable);
 
diff --git a/test/engine/imap/transport/imap-client-connection-test.vala b/test/engine/imap/transport/imap-client-connection-test.vala
index 56f6029b..c98f0dc5 100644
--- a/test/engine/imap/transport/imap-client-connection-test.vala
+++ b/test/engine/imap/transport/imap-client-connection-test.vala
@@ -8,6 +8,14 @@
 class Geary.Imap.ClientConnectionTest : TestCase {
 
 
+    private class TestCommand : Command {
+
+        public TestCommand() {
+            base("TEST");
+        }
+
+    }
+
     private TestServer? server = null;
 
 
@@ -88,7 +96,7 @@ class Geary.Imap.ClientConnectionTest : TestCase {
 
         assert_true(test_article.is_in_idle(), "Post idle command timeout");
 
-        var command = new Command("TEST");
+        var command = new TestCommand();
         test_article.send_command(command);
         command.wait_until_complete.begin(null, this.async_complete_full);
         command.wait_until_complete.end(async_result());
@@ -121,7 +129,7 @@ class Geary.Imap.ClientConnectionTest : TestCase {
         test_article.connect_async.begin(null, this.async_complete_full);
         test_article.connect_async.end(async_result());
 
-        var command = new Command("TEST");
+        var command = new TestCommand();
         command.response_timed_out.connect(() => { timed_out = true; });
 
         test_article.send_command(command);