diff --git a/core/modules/migrate/src/Entity/Migration.php b/core/modules/migrate/src/Entity/Migration.php
index 3357205..f07ba40 100644
--- a/core/modules/migrate/src/Entity/Migration.php
+++ b/core/modules/migrate/src/Entity/Migration.php
@@ -14,6 +14,7 @@
 use Drupal\migrate\MigrateSkipRowException;
 use Drupal\migrate\Plugin\MigrateIdMapInterface;
 use Drupal\migrate\Plugin\RequirementsInterface;
+use Drupal\Component\Utility\NestedArray;
 
 /**
  * Defines the Migration entity.
@@ -406,8 +407,14 @@ public function setProcess(array $process) {
   /**
    * {@inheritdoc}
    */
-  public function setProcessOfProperty($field_name, $process) {
-    $this->process[$field_name] = $process;
+  public function setProcessOfProperty($field_name, $process, $merge = TRUE) {
+    if (isset($this->process[$field_name]) && is_array($process) && $merge) {
+      $this->process = NestedArray::mergeDeepArray([$this->process, [$field_name => $process]], TRUE);
+    }
+    else {
+      $this->process[$field_name] = $process;
+    }
+    return $this;
   }
 
   /**
diff --git a/core/modules/migrate/src/Entity/MigrationInterface.php b/core/modules/migrate/src/Entity/MigrationInterface.php
index 4e795bf..ca9ac03 100644
--- a/core/modules/migrate/src/Entity/MigrationInterface.php
+++ b/core/modules/migrate/src/Entity/MigrationInterface.php
@@ -188,26 +188,31 @@ public function getMigrationResult();
   public function getProcess();
 
   /**
-   * Set the process for an individual destination field.
+   * Set the current configuration describing the process plugins.
    *
-   * @param string $field_name
-   *   The field name of which to set the process.
-   * @param $process
-   *   An array of process data.
+   * @param array $process
+   *   The configuration describing the process plugins.
    *
-   * @see Drupal\migrate_drupal\Plugin\migrate\load\LoadEntity::processLinkField().
+   * @return $this
    */
-  public function setProcessOfProperty($field_name, $process);
+  public function setProcess(array $process);
 
   /**
-   * Set the current configuration describing the process plugins.
+   * Set the process for an individual destination field.
    *
+   * @param string $field_name
+   *   The field name of which to set the process.
    * @param array $process
-   *   The configuration describing the process plugins.
+   *   An array of process data.
+   * @param boolean $merge
+   *   (optional) TRUE if we should merge the process arrays otherwise FALSE.
    *
    * @return $this
+   *   The migration entity.
+   *
+   * @see Drupal\migrate_drupal\Plugin\migrate\load\LoadEntity::processLinkField().
    */
-  public function setProcess(array $process);
+  public function setProcessOfProperty($field_name, $process, $merge = TRUE);
 
   /**
    * Get the current system of record of the migration.