diff -u b/core/modules/migrate/src/Event/MigrateMemoryLimitEvent.php b/core/modules/migrate/src/Event/MigrateMemoryLimitEvent.php
--- b/core/modules/migrate/src/Event/MigrateMemoryLimitEvent.php
+++ b/core/modules/migrate/src/Event/MigrateMemoryLimitEvent.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\migrate\Event;
 
-use Symfony\Component\EventDispatcher\Event;
+use Drupal\Component\EventDispatcher\Event;
 
 /**
  * Wraps a memory limit event for event listeners.
diff -u b/core/modules/migrate/src/MemoryManager.php b/core/modules/migrate/src/MemoryManager.php
--- b/core/modules/migrate/src/MemoryManager.php
+++ b/core/modules/migrate/src/MemoryManager.php
@@ -94,7 +94,7 @@
    */
   protected function dispatchEvent($phase) {
     $event = new MigrateMemoryLimitEvent($this->getUsageRatio(), $this->getUsageInBytes(), $this->getLimit(), $phase);
-    $this->dispatcher->dispatch(MigrateEvents::MEMORY_LIMIT, $event);
+    $this->dispatcher->dispatch($event, MigrateEvents::MEMORY_LIMIT);
   }
 
   /**
diff -u b/core/modules/migrate/tests/src/Unit/MigrateExecutableTest.php b/core/modules/migrate/tests/src/Unit/MigrateExecutableTest.php
--- b/core/modules/migrate/tests/src/Unit/MigrateExecutableTest.php
+++ b/core/modules/migrate/tests/src/Unit/MigrateExecutableTest.php
@@ -60,8 +60,7 @@
     $this->migration = $this->getMigration();
     $this->message = $this->createMock('Drupal\migrate\MigrateMessageInterface');
     $event_dispatcher = $this->createMock('Symfony\Contracts\EventDispatcher\EventDispatcherInterface');
-    $this->memoryManager = $this->createMock('Drupal\migrate\MemoryManagerInterface');
-    $this->executable = new TestMigrateExecutable($this->migration, $this->message, $event_dispatcher, $this->memoryManager);
+    $this->executable = new TestMigrateExecutable($this->migration, $this->message, $event_dispatcher);
     $this->executable->setStringTranslation($this->getStringTranslationStub());
   }
 
@@ -78,7 +77,8 @@
     $this->migration = $this->getMigration();
     $this->message = $this->createMock('Drupal\migrate\MigrateMessageInterface');
     $this->eventDispatcher = $this->createMock('Symfony\Contracts\EventDispatcher\EventDispatcherInterface');
-    $this->executable = new TestMigrateExecutable($this->migration, $this->message, $this->eventDispatcher);
+    $this->memoryManager = $this->createMock('Drupal\migrate\MemoryManagerInterface');
+    $this->executable = new TestMigrateExecutable($this->migration, $this->message, $this->eventDispatcher, $this->memoryManager);
     $this->executable->setStringTranslation($this->getStringTranslationStub());
   }
 
@@ -162,6 +162,9 @@
     $this->idMap->expects($this->never())
       ->method('saveIdMapping');
 
+    $this->memoryManager->method('ensureMemory')
+      ->willReturn(TRUE);
+
     $this->assertSame(MigrationInterface::RESULT_COMPLETED, $this->executable->import());
   }
 
@@ -179,9 +182,6 @@
     $this->idMap->expects($this->never())
       ->method('saveIdMapping');
 
-    $this->memoryManager->method('ensureMemory')
-      ->willReturn(TRUE);
-
     $this->assertSame(MigrationInterface::RESULT_COMPLETED, $this->executable->import());
   }
 
@@ -218,6 +218,9 @@
       ->method('getDestinationPlugin')
       ->willReturn($destination);
 
+    $this->memoryManager->method('ensureMemory')
+      ->willReturn(TRUE);
+
     $this->assertSame(MigrationInterface::RESULT_COMPLETED, $this->executable->import());
   }
 
@@ -239,9 +242,6 @@
       ->method('display')
       ->with('New object was not saved, no error provided');
 
-    $this->memoryManager->method('ensureMemory')
-      ->willReturn(TRUE);
-
     $this->assertSame(MigrationInterface::RESULT_COMPLETED, $this->executable->import());
   }
 
@@ -269,6 +269,9 @@
     $this->idMap->expects($this->never())
       ->method('lookupDestinationIds');
 
+    $this->memoryManager->method('ensureMemory')
+      ->willReturn(TRUE);
+
     $this->assertSame(MigrationInterface::RESULT_COMPLETED, $this->executable->import());
   }
 
@@ -345,9 +348,6 @@
     $this->idMap->expects($this->never())
       ->method('lookupDestinationIds');
 
-    $this->memoryManager->method('ensureMemory')
-      ->willReturn(TRUE);
-
     $this->assertSame(MigrationInterface::RESULT_COMPLETED, $this->executable->import());
   }
 
@@ -402,9 +402,6 @@
       ->method('display')
       ->with($exception_message);
 
-    $this->memoryManager->method('ensureMemory')
-      ->willReturn(TRUE);
-
     $this->assertSame(MigrationInterface::RESULT_COMPLETED, $this->executable->import());
   }