diff --git a/core/lib/Drupal/Core/Password/PhpPassword.php b/core/lib/Drupal/Core/Password/PhpPassword.php
index a26b8e4..3e02b8f 100644
--- a/core/lib/Drupal/Core/Password/PhpPassword.php
+++ b/core/lib/Drupal/Core/Password/PhpPassword.php
@@ -13,7 +13,14 @@
  * Secure password hashing functions based on PHP (>=5.5.0) password hashing
  * functions.
  *
+ * NOTE: Because password hashing functions are available only since PHP 5.5, on
+ * PHP 5.4 the compatibility is assured by the 'password_compat' library (see
+ * https://github.com/ircmaxell/password_compat).
+ *
  * @see http://php.net/manual/en/ref.password.php
+ * @see https://github.com/ircmaxell/password_compat
+ *
+ * @todo Remove 'password_compat' library when Drupal will require PHP >= 5.5.0
  */
 class PhpPassword implements PasswordInterface {
 
@@ -67,7 +74,7 @@ public function check($password, UserInterface $account) {
       $stored_hash = substr($stored_hash, 2);
       $password = $this->drupal7Password->hash($password);
     }
-    // Password migrated from Drupal 6.
+    // MD5 migrated password (Drupal 6).
     elseif (substr($stored_hash, 0, 2) == 'U$') {
       $stored_hash = substr($stored_hash, 1);
       $password = md5($password);
diff --git a/core/modules/migrate/src/MigratePassword.php b/core/modules/migrate/src/MigratePassword.php
index 796c7f1..2d45f41 100644
--- a/core/modules/migrate/src/MigratePassword.php
+++ b/core/modules/migrate/src/MigratePassword.php
@@ -8,12 +8,13 @@
 namespace Drupal\migrate;
 
 use Drupal\Core\Password\PasswordInterface;
+use Drupal\migrate\Entity\MigrationInterface;
 use Drupal\user\UserInterface;
 
 /**
- * Replaces the original 'password' service in order to prefix the MD5 re-hashed
- * passwords with the 'U' flag. The new salted hash is recreated on first login
- * similarly to the D6->D7 upgrade path.
+ * Replaces the original 'password' service in order to prefix the MD5 or
+ * Drupal 7 re-hashed passwords. The new salted hash will be recreated on first
+ * login similarly to the D6->D7 upgrade path.
  */
 class MigratePassword implements PasswordInterface {
 
@@ -26,10 +27,19 @@ class MigratePassword implements PasswordInterface {
 
   /**
    * Indicates if MD5 password prefixing is enabled.
+   *
+   * @var bool
    */
   protected $enabled = FALSE;
 
   /**
+   * The current migration.
+   *
+   * @var \Drupal\migrate\Entity\MigrationInterface
+   */
+  protected $migration;
+
+  /**
    * Builds the replacement password service class.
    *
    * @param \Drupal\Core\Password\PasswordInterface $original_password
@@ -66,13 +76,11 @@ public function hash($password) {
       if (preg_match('/^[0-9a-f]{32}$/', $password)) {
         $hash = 'U' . $hash;
       }
-      // @todo Is this enough? Maybe we should pass and test somehow the current
-      // migration source to detect a Drupal 7 source. This can be done by
-      // injecting the current migration when enabling prefixing in
-      // Drupal\migrate\Plugin\migrate\destination\EntityUser. In that case
-      // ::enableMd5Prefixing() needs to be renamed. Or pass the migration into
-      // constructor? How?
-      if (substr($password, 0, 3) == '$S$') {
+      // Prefix user hashed passwords coming from Drupal 7.
+      // @todo This needs testing when D7->D8 migration will be merged into main
+      //   repository.
+      $source = $this->migration->getSourcePlugin()->getPluginId();
+      if (substr($password, 0, 3) == '$S$' && $source == 'd7_user') {
         $hash = 'D7' . $hash;
       }
     }
@@ -81,17 +89,27 @@ public function hash($password) {
   }
 
   /**
-   * Enables the MD5 password prefixing.
+   * Enables password prefixing.
    */
-  public function enableMd5Prefixing() {
+  public function enablePrefixing() {
     $this->enabled = TRUE;
   }
 
   /**
-   * Disables the MD5 password prefixing.
+   * Disables password prefixing.
    */
-  public function disableMd5Prefixing() {
+  public function disablePrefixing() {
     $this->enabled = FALSE;
   }
 
+  /**
+   * Sets the current migration.
+   *
+   * @param \Drupal\migrate\Entity\MigrationInterface $migration
+   *   The current migration.
+   */
+  public function setMigration(MigrationInterface $migration) {
+    $this->migration = $migration;
+  }
+
 }
diff --git a/core/modules/migrate/src/MigrateServiceProvider.php b/core/modules/migrate/src/MigrateServiceProvider.php
index 78a60bb..705f9d2 100644
--- a/core/modules/migrate/src/MigrateServiceProvider.php
+++ b/core/modules/migrate/src/MigrateServiceProvider.php
@@ -12,10 +12,10 @@
 
 /**
  * Swaps the original 'password' service in order to handle password hashing for
- * user migrations that have passwords hashed to MD5.
+ * user migrations that have passwords hashed with MD5 or Drupal 7 passwords.
  *
  * @see \Drupal\migrate\MigratePassword
- * @see \Drupal\Core\Password\PhpassHashedPassword
+ * @see \Drupal\Core\Password\PhpPassword
  */
 class MigrateServiceProvider implements ServiceModifierInterface {
 
diff --git a/core/modules/migrate/src/Plugin/migrate/destination/EntityUser.php b/core/modules/migrate/src/Plugin/migrate/destination/EntityUser.php
index 786988f..34fd890 100644
--- a/core/modules/migrate/src/Plugin/migrate/destination/EntityUser.php
+++ b/core/modules/migrate/src/Plugin/migrate/destination/EntityUser.php
@@ -13,7 +13,6 @@
 use Drupal\migrate\Entity\MigrationInterface;
 use Drupal\migrate\MigrateException;
 use Drupal\migrate\MigratePassword;
-use Drupal\migrate\Plugin\MigratePluginManager;
 use Drupal\migrate\Row;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -79,12 +78,14 @@ public static function create(ContainerInterface $container, array $configuratio
 
   /**
    * {@inheritdoc}
+   *
    * @throws \Drupal\migrate\MigrateException
    */
   public function import(Row $row, array $old_destination_id_values = array()) {
     if ($this->password) {
       if ($this->password instanceof MigratePassword) {
-        $this->password->enableMd5Prefixing();
+        $this->password->setMigration($this->migration);
+        $this->password->enablePrefixing();
       }
       else {
         throw new MigrateException('Password service has been altered by another module, aborting.');
@@ -92,7 +93,7 @@ public function import(Row $row, array $old_destination_id_values = array()) {
     }
     $ids = parent::import($row, $old_destination_id_values);
     if ($this->password) {
-      $this->password->disableMd5Prefixing();
+      $this->password->disablePrefixing();
     }
 
     return $ids;