diff --git a/core/modules/block/block.install b/core/modules/block/block.install
index 470d3bc..a5bd3c4 100644
--- a/core/modules/block/block.install
+++ b/core/modules/block/block.install
@@ -368,10 +368,15 @@ function block_update_8005() {
   // Take over the extracted and serialized value in {_d7_users_data} as-is.
   $query->addField('ud', 'value');
   $query->addExpression('1', 'serialized');
+  $query->condition('name', 'block');
 
   db_insert('users_data')
     ->from($query)
     ->execute();
+
+  db_delete('_d7_users_data')
+    ->condition('name', 'block')
+    ->execute();
 }
 
 /**
diff --git a/core/modules/contact/contact.install b/core/modules/contact/contact.install
index 845aa1f..879c6ab 100644
--- a/core/modules/contact/contact.install
+++ b/core/modules/contact/contact.install
@@ -91,6 +91,7 @@ function contact_update_8003() {
     $query->addExpression("'contact'", 'module');
     $query->addExpression("'enabled'", 'name');
     $query->condition('value', $serialized_setting);
+    $query->condition('name', 'contact');
     $query->addExpression($enabled, 'value');
     $query->addExpression(0, 'serialized');
 
@@ -98,6 +99,9 @@ function contact_update_8003() {
       ->from($query)
       ->execute();
   }
+  db_delete('_d7_users_data')
+    ->condition('name', 'contact')
+    ->execute();
 }
 
 /**
diff --git a/core/modules/overlay/overlay.install b/core/modules/overlay/overlay.install
index a2ef679..c8e9f3a 100644
--- a/core/modules/overlay/overlay.install
+++ b/core/modules/overlay/overlay.install
@@ -41,6 +41,7 @@ function overlay_update_8000() {
     $query->addExpression("'overlay'", 'module');
     $query->addExpression("'enabled'", 'name');
     $query->condition('value', $serialized_setting);
+    $query->condition('name', 'overlay');
     $query->addExpression($enabled, 'value');
     $query->addExpression(0, 'serialized');
 
@@ -54,10 +55,15 @@ function overlay_update_8000() {
   $query->addExpression("'overlay'", 'module');
   $query->addExpression("'message_dismissed'", 'name');
   $query->condition('value', serialize('1'));
+  $query->condition('name', 'overlay_message_dismissed');
   $query->addExpression(1, 'value');
   $query->addExpression(0, 'serialized');
 
   db_insert('users_data')
     ->from($query)
     ->execute();
+
+  db_delete('_d7_users_data')
+    ->condition('name', array('overlay', 'overlay_message_dismissed'))
+    ->execute();
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/FilledStandardUpgradePathTest.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/FilledStandardUpgradePathTest.php
index e1df73e..1644265 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/FilledStandardUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/FilledStandardUpgradePathTest.php
@@ -29,6 +29,7 @@ public function setUp() {
     // Path to the database dump files.
     $this->databaseDumpFiles = array(
       drupal_get_path('module', 'system') . '/tests/upgrade/drupal-7.filled.standard_all.database.php.gz',
+      drupal_get_path('module', 'system') . '/tests/upgrade/drupal-7.user_data.database.php',
     );
     parent::setUp();
   }
@@ -96,5 +97,28 @@ public function testFilledStandardUpgrade() {
     $blog_type = node_type_load('blog');
     $this->assertEqual($blog_type->module, 'node', "Content type 'blog' has been reassigned from the blog module to the node module.");
     $this->assertEqual($blog_type->base, 'node_content', "The base string used to construct callbacks corresponding to content type 'Blog' has been reassigned to 'node_content'.");
+
+    // Check that user data has been migrated correctly.
+    $query = db_query('SELECT * FROM {users_data}');
+
+    $userdata = array();
+    $i = 0;
+    foreach ($query as $row) {
+      $i++;
+      $userdata[$row->uid][$row->module][$row->name] = $row;
+    }
+    // Check that the correct amount of rows exist.
+    $this->assertEqual($i, 5);
+    // Check that the data has been converted correctly.
+    $this->assertEqual($userdata[1]['contact']['enabled']->value, 1);
+    $this->assertEqual($userdata[1]['contact']['enabled']->serialized, 0);
+    $this->assertEqual($userdata[2]['contact']['enabled']->value, 0);
+    $this->assertEqual($userdata[1]['overlay']['enabled']->value, 1);
+    $this->assertEqual($userdata[2]['overlay']['enabled']->value, 1);
+    $this->assertEqual($userdata[1]['overlay']['message_dismissed']->value, 1);
+    $this->assertFalse(isset($userdata[2]['overlay']['message_dismissed']));
+
+    // Make sure that only the garbage is remaining in the helper table.
+    $this->assertEqual(db_query('SELECT COUNT(*) FROM {_d7_users_data}')->fetchField(), 2);
   }
 }
diff --git a/core/modules/system/tests/upgrade/drupal-7.user_data.database.php b/core/modules/system/tests/upgrade/drupal-7.user_data.database.php
new file mode 100644
index 0000000..b17fc64
--- /dev/null
+++ b/core/modules/system/tests/upgrade/drupal-7.user_data.database.php
@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * @file
+ * Database additions for role tests. Used in
+ * \Drupal\system\Tests\Upgrade\FilledStandardUpgradePathTest.
+ *
+ * This dump only contains data and schema components relevant for user data
+ * upgrade tests. The drupal-7.filed.database.php.gz file is imported before
+ * this dump, so the two form the database structure expected in tests
+ * altogether.
+ */
+
+db_update('users')
+  ->condition('uid', 1)
+  ->fields(array(
+    'data' => serialize(array(
+      'contact' => '1',
+      'overlay_message_dismissed' => '1',
+      'overlay' => '1',
+      'garbage' => 'data',
+    )),
+  ))
+  ->execute();
+
+db_update('users')
+  ->condition('uid', 2)
+  ->fields(array(
+    'data' => serialize(array(
+      'contact' => '0',
+      'overlay' => '1',
+      'more' => array('garbage', 'data'),
+    )),
+  ))
+  ->execute();
diff --git a/core/modules/user/user.install b/core/modules/user/user.install
index 480092e..7b2dd8a 100644
--- a/core/modules/user/user.install
+++ b/core/modules/user/user.install
@@ -735,7 +735,7 @@ function user_update_8010() {
         'serialize' => TRUE,
       ),
     ),
-    'primary key' => array('uid'),
+    'primary key' => array('uid', 'name'),
     'foreign keys' => array(
       'uid' => array('users' => 'uid'),
     ),