diff --git a/src/Plugin/VersionNegotiation/VersionByRel.php b/src/Plugin/VersionNegotiation/VersionByRel.php
index aa39b83..92b72de 100644
--- a/src/Plugin/VersionNegotiation/VersionByRel.php
+++ b/src/Plugin/VersionNegotiation/VersionByRel.php
@@ -8,7 +8,6 @@ use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
 use Drupal\jsonapi\Revisions\InvalidVersionIdentifierException;
 use Drupal\jsonapi\Revisions\PluginNegotiationBase;
 use Drupal\jsonapi\Revisions\VersionNegotiationInterface;
-use Drupal\jsonapi\Revisions\VersionNegotiationManager;
 
 /**
  * Revision ID implementation for the current or latest revisions.
diff --git a/src/ResourceType/ResourceType.php b/src/ResourceType/ResourceType.php
index 40bda08..ec7bbbd 100644
--- a/src/ResourceType/ResourceType.php
+++ b/src/ResourceType/ResourceType.php
@@ -274,7 +274,7 @@ class ResourceType {
    * @param bool $is_mutable
    *   (optional) Whether the resource type is mutable.
    * @param bool $is_versionable
-  +   (optional) Whether the resource type is versionable.
+   *   (optional) Whether the resource type is versionable.
    * @param array $field_mapping
    *   (optional) The field mapping to use.
    */
diff --git a/src/Revisions/PluginNegotiationBase.php b/src/Revisions/PluginNegotiationBase.php
index 2bc4eb9..9a56a70 100644
--- a/src/Revisions/PluginNegotiationBase.php
+++ b/src/Revisions/PluginNegotiationBase.php
@@ -76,7 +76,7 @@ abstract class PluginNegotiationBase extends PluginBase implements ContainerFact
    *
    * @param \Drupal\Core\Entity\EntityInterface $entity
    *   The entity for which to load a revision.
-   * @param $revision_id
+   * @param int $revision_id
    *   The revision ID to be loaded.
    *
    * @return \Drupal\Core\Entity\EntityInterface|null
@@ -97,7 +97,7 @@ abstract class PluginNegotiationBase extends PluginBase implements ContainerFact
   /**
    * Helper method that ensures that a version exists.
    *
-   * @param  int|\Drupal\Core\Entity\EntityInterface $revision
+   * @param int|\Drupal\Core\Entity\EntityInterface $revision
    *   A revision ID, or NULL if one was not found.
    *
    * @return int|\Drupal\Core\Entity\EntityInterface
diff --git a/src/Revisions/VersionNotFoundException.php b/src/Revisions/VersionNotFoundException.php
index 1f6d901..aa12bf4 100644
--- a/src/Revisions/VersionNotFoundException.php
+++ b/src/Revisions/VersionNotFoundException.php
@@ -2,8 +2,6 @@
 
 namespace Drupal\jsonapi\Revisions;
 
-use Throwable;
-
 /**
  * Used when a version ID is valid, but the requested version does not exist.
  *
@@ -14,8 +12,8 @@ class VersionNotFoundException extends \InvalidArgumentException {
   /**
    * {@inheritdoc}
    */
-  public function __construct(string $message = 'The identified version could not be found.', int $code = 0, \Throwable $previous = NULL) {
-    parent::__construct($message, $code, $previous);
+  public function __construct($message = NULL, $code = 0, \Exception $previous = NULL) {
+    parent::__construct(!is_null($message) ? $message : 'The identified version could not be found.', $code, $previous);
   }
 
 }