diff --git a/lib/Config/Migrator.php b/lib/Config/Migrator.php
index ebfa554301..747598d74b 100644
--- a/lib/Config/Migrator.php
+++ b/lib/Config/Migrator.php
@@ -59,7 +59,7 @@ class Migrator {
       'id mediumint(9) NOT NULL AUTO_INCREMENT,',
       'name varchar(90) NOT NULL,',
       'type varchar(90) NOT NULL DEFAULT "default",',
-      'description varchar(250) NOT NULL,',
+      'description varchar(250) NOT NULL DEFAULT "",',
       'created_at TIMESTAMP NOT NULL DEFAULT 0,',
       'deleted_at TIMESTAMP NULL DEFAULT NULL,',
       'updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,',
@@ -124,8 +124,8 @@ class Migrator {
     $attributes = array(
       'id mediumint(9) NOT NULL AUTO_INCREMENT,',
       'wp_user_id bigint(20) NULL,',
-      'first_name tinytext NOT NULL,',
-      'last_name tinytext NOT NULL,',
+      'first_name tinytext NOT NULL DEFAULT "",',
+      'last_name tinytext NOT NULL DEFAULT "",',
       'email varchar(150) NOT NULL,',
       'status varchar(12) NOT NULL DEFAULT "unconfirmed",',
       'created_at TIMESTAMP NOT NULL DEFAULT 0,',
@@ -156,7 +156,7 @@ class Migrator {
       'id mediumint(9) NOT NULL AUTO_INCREMENT,',
       'subscriber_id mediumint(9) NOT NULL,',
       'custom_field_id mediumint(9) NOT NULL,',
-      'value varchar(255) NOT NULL,',
+      'value varchar(255) NOT NULL DEFAULT "",',
       'created_at TIMESTAMP NOT NULL DEFAULT 0,',
       'updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,',
       'PRIMARY KEY  (id),',
@@ -168,13 +168,13 @@ class Migrator {
   function newsletters() {
     $attributes = array(
       'id mediumint(9) NOT NULL AUTO_INCREMENT,',
-      'subject varchar(250) NOT NULL,',
+      'subject varchar(250) NOT NULL DEFAULT "",',
       'type varchar(20) NOT NULL DEFAULT "standard",',
-      'sender_address varchar(150) NOT NULL,',
-      'sender_name varchar(150) NOT NULL,',
-      'reply_to_address varchar(150) NOT NULL,',
-      'reply_to_name varchar(150) NOT NULL,',
-      'preheader varchar(250) NOT NULL,',
+      'sender_address varchar(150) NOT NULL DEFAULT "",',
+      'sender_name varchar(150) NOT NULL DEFAULT "",',
+      'reply_to_address varchar(150) NOT NULL DEFAULT "",',
+      'reply_to_name varchar(150) NOT NULL DEFAULT "",',
+      'preheader varchar(250) NOT NULL DEFAULT "",',
       'body longtext,',
       'created_at TIMESTAMP NOT NULL DEFAULT 0,',
       'deleted_at TIMESTAMP NULL DEFAULT NULL,',
@@ -217,7 +217,7 @@ class Migrator {
       'id mediumint(9) NOT NULL AUTO_INCREMENT,',
       'newsletter_id mediumint(9) NOT NULL,',
       'option_field_id mediumint(9) NOT NULL,',
-      'value varchar(255) NOT NULL,',
+      'value varchar(255) NOT NULL DEFAULT "",',
       'created_at TIMESTAMP NOT NULL DEFAULT 0,',
       'updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,',
       'PRIMARY KEY  (id),',
diff --git a/lib/Subscribers/ImportExport/Import/MailChimp.php b/lib/Subscribers/ImportExport/Import/MailChimp.php
index 6192512525..11209c9059 100644
--- a/lib/Subscribers/ImportExport/Import/MailChimp.php
+++ b/lib/Subscribers/ImportExport/Import/MailChimp.php
@@ -121,7 +121,8 @@ class MailChimp {
   function getDataCenter($APIKey) {
     if (!preg_match('/-[a-zA-Z0-9]{3,}/', $APIKey)) return false;
     // double parantheses: http://phpsadness.com/sad/51
-    return end((explode('-', $APIKey)));
+    $key_parts = explode('-', $APIKey);
+    return end($key_parts);
   }
 
   function getAPIKey($APIKey) {
diff --git a/tests/unit/Models/NewsletterTest.php b/tests/unit/Models/NewsletterTest.php
index 58be6e8aef..4ff9ab77a0 100644
--- a/tests/unit/Models/NewsletterTest.php
+++ b/tests/unit/Models/NewsletterTest.php
@@ -2,6 +2,7 @@
 
 use MailPoet\Models\Newsletter;
 use MailPoet\Models\Segment;
+use MailPoet\Models\Subscriber;
 use MailPoet\Models\SendingQueue;
 use MailPoet\Models\NewsletterSegment;
 use MailPoet\Models\NewsletterOptionField;
@@ -111,10 +112,17 @@ class NewsletterTest extends MailPoetTest {
     $sending_queue = SendingQueue::create();
     $sending_queue->newsletter_id = $this->newsletter->id;
     $sending_queue->save();
+
+    $subscriber = Subscriber::createOrUpdate(array(
+      'email' => 'john.doe@mailpoet.com'
+    ));
+
     $opens = StatisticsOpens::create();
+    $opens->subscriber_id = $subscriber->id;
     $opens->newsletter_id = $this->newsletter->id;
     $opens->queue_id = $sending_queue->id;
     $opens->save();
+
     $newsletter->queue = $newsletter->getQueue()->asArray();
     $statistics = $newsletter->getStatistics();
     expect($statistics->opened)->equals(1);
diff --git a/tests/unit/Router/NewslettersTest.php b/tests/unit/Router/NewslettersTest.php
index c11545640b..5a0e6206c5 100644
--- a/tests/unit/Router/NewslettersTest.php
+++ b/tests/unit/Router/NewslettersTest.php
@@ -53,8 +53,10 @@ class NewslettersTest extends MailPoetTest {
 
   function testItCanSaveAnExistingNewsletter() {
     $router = new Newsletters();
-    $newsletter_data = $this->newsletter->asArray();
-    $newsletter_data['subject'] = 'My Updated Newsletter';
+    $newsletter_data = array(
+      'id' => $this->newsletter->id,
+      'subject' => 'My Updated Newsletter'
+    );
 
     $response = $router->save($newsletter_data);
     expect($response['result'])->true();