diff --git a/src/Enums/MetaData.php b/src/Enums/MetaData.php
index 5a77c523..4d10e758 100644
--- a/src/Enums/MetaData.php
+++ b/src/Enums/MetaData.php
@@ -4,8 +4,8 @@
 
 class MetaData
 {
-    const AGGREGATE_ROOT_UUID = 'aggregate-root-uuid';
-    const STORED_EVENT_ID = 'stored-event-id';
-    const CREATED_AT = 'created-at';
-    const AGGREGATE_ROOT_VERSION = 'aggregate-root-version';
+    public const AGGREGATE_ROOT_UUID = 'aggregate-root-uuid';
+    public const STORED_EVENT_ID = 'stored-event-id';
+    public const CREATED_AT = 'created-at';
+    public const AGGREGATE_ROOT_VERSION = 'aggregate-root-version';
 }
diff --git a/src/EventSerializers/JsonEventSerializer.php b/src/EventSerializers/JsonEventSerializer.php
index 9999b695..07f674af 100644
--- a/src/EventSerializers/JsonEventSerializer.php
+++ b/src/EventSerializers/JsonEventSerializer.php
@@ -14,7 +14,7 @@ public function __construct()
     {
         $encoders = [new JsonEncoder()];
         $normalizers = array_map(
-            fn ($className) => new $className,
+            fn ($className) => new $className(),
             config('event-sourcing.event_normalizers')
         );
 
diff --git a/src/Snapshots/EloquentSnapshotRepository.php b/src/Snapshots/EloquentSnapshotRepository.php
index 1ac2fdf4..f7806508 100644
--- a/src/Snapshots/EloquentSnapshotRepository.php
+++ b/src/Snapshots/EloquentSnapshotRepository.php
@@ -12,7 +12,7 @@ public function __construct()
     {
         $this->snapshotModel = (string)config('event-sourcing.snapshot_model', EloquentSnapshot::class);
 
-        if (! new $this->snapshotModel instanceof EloquentSnapshot) {
+        if (! new $this->snapshotModel() instanceof EloquentSnapshot) {
             throw new InvalidEloquentSnapshotModel("The class {$this->snapshotModel} must extend EloquentSnapshot");
         }
     }
diff --git a/src/StoredEvents/Repositories/EloquentStoredEventRepository.php b/src/StoredEvents/Repositories/EloquentStoredEventRepository.php
index f3c63869..8966f29f 100644
--- a/src/StoredEvents/Repositories/EloquentStoredEventRepository.php
+++ b/src/StoredEvents/Repositories/EloquentStoredEventRepository.php
@@ -21,7 +21,7 @@ public function __construct()
     {
         $this->storedEventModel = (string) config('event-sourcing.stored_event_model', EloquentStoredEvent::class);
 
-        if (! new $this->storedEventModel instanceof EloquentStoredEvent) {
+        if (! new $this->storedEventModel() instanceof EloquentStoredEvent) {
             throw new InvalidEloquentStoredEventModel("The class {$this->storedEventModel} must extend EloquentStoredEvent");
         }
     }
diff --git a/src/Support/ModelIdentifierNormalizer.php b/src/Support/ModelIdentifierNormalizer.php
index 0b105e9f..ff94c146 100644
--- a/src/Support/ModelIdentifierNormalizer.php
+++ b/src/Support/ModelIdentifierNormalizer.php
@@ -13,7 +13,7 @@
 class ModelIdentifierNormalizer implements NormalizerInterface, DenormalizerInterface
 {
     use SerializesAndRestoresModelIdentifiers;
-    
+
     /**
      * @inheritdoc
      */
@@ -22,10 +22,10 @@ public function normalize($object, string $format = null, array $context = [])
         if (! $this->supportsNormalization($object)) {
             throw new InvalidArgumentException('Cannot serialize an object that is not a QueueableEntity or QueueableCollection in ModelIdentifierNormalizer.');
         }
-    
+
         return $this->getSerializedPropertyValue($object);
     }
-    
+
     /**
      * @inheritdoc
      */
@@ -33,7 +33,7 @@ public function supportsNormalization($data, string $format = null)
     {
         return ($data instanceof QueueableEntity || $data instanceof QueueableCollection);
     }
-    
+
     /**
      * @inheritdoc
      */
@@ -42,10 +42,10 @@ public function denormalize($data, $class, string $format = null, array $context
         $identifier = $data instanceof ModelIdentifier
             ? $data
             : new ModelIdentifier($data['class'], $data['id'], $data['relations'], $data['connection']);
-        
+
         return $this->getRestoredPropertyValue($identifier);
     }
-    
+
     /**
      * @inheritdoc
      */
@@ -54,13 +54,13 @@ public function supportsDenormalization($data, $type, string $format = null)
         return $this->normalizedDataIsModelIdentifier($data)
             && $this->isNormalizedToModelIdentifier($type);
     }
-    
+
     protected function normalizedDataIsModelIdentifier($data): bool
     {
         return $data instanceof ModelIdentifier
             || isset($data['class'], $data['id'], $data['relations'], $data['connection']);
     }
-    
+
     protected function isNormalizedToModelIdentifier($class): bool
     {
         return is_a($class, QueueableEntity::class, true)
diff --git a/tests/AggregateRoots/AggregatePartialTest.php b/tests/AggregateRoots/AggregatePartialTest.php
index 036e7357..127d9c0e 100644
--- a/tests/AggregateRoots/AggregatePartialTest.php
+++ b/tests/AggregateRoots/AggregatePartialTest.php
@@ -23,7 +23,7 @@ public function test_entities()
             ->addItem('test 2')
             ->persist();
 
-        $this->assertDatabaseCount((new EloquentStoredEvent)->getTable(), 2);
+        $this->assertDatabaseCount((new EloquentStoredEvent())->getTable(), 2);
 
         $cart::retrieve(self::CART_UUID);
 
@@ -87,7 +87,7 @@ public function addItem(string $name): self
 
     public function clear(): self
     {
-        $this->recordThat(new CartCleared);
+        $this->recordThat(new CartCleared());
 
         return $this;
     }
diff --git a/tests/AggregateRoots/CommandHandlerTest.php b/tests/AggregateRoots/CommandHandlerTest.php
index ada466ae..d69c9bbf 100644
--- a/tests/AggregateRoots/CommandHandlerTest.php
+++ b/tests/AggregateRoots/CommandHandlerTest.php
@@ -69,7 +69,7 @@ public function __construct()
 
     public function clear(ClearCart $clearCart): self
     {
-        $this->recordThat(new CartClearedForCommand);
+        $this->recordThat(new CartClearedForCommand());
 
         return $this;
     }
diff --git a/tests/EloquentStoredEventRepositoryTest.php b/tests/EloquentStoredEventRepositoryTest.php
index 6150ab4f..23acba5c 100644
--- a/tests/EloquentStoredEventRepositoryTest.php
+++ b/tests/EloquentStoredEventRepositoryTest.php
@@ -29,15 +29,15 @@ public function it_can_get_the_latest_version_id_for_a_given_aggregate_uuid()
         $this->assertEquals(1, $eloquentStoredEventRepository->getLatestAggregateVersion('uuid-2'));
         $this->assertEquals(2, $eloquentStoredEventRepository->getLatestAggregateVersion('uuid-1'));
     }
-    
+
     /** @test */
     public function it_sets_the_original_event_on_persist()
     {
         $eloquentStoredEventRepository = app(EloquentStoredEventRepository::class);
-        
+
         $originalEvent = new MoneyAdded(100);
         $storedEvent = $eloquentStoredEventRepository->persist($originalEvent, 'uuid-1', 1);
-        
+
         $this->assertSame($originalEvent, $storedEvent->event);
     }
 }