diff --git a/src/Adapter/AdapterInterface.php b/src/Adapter/AdapterInterface.php
index cc53933..a31ba44 100644
--- a/src/Adapter/AdapterInterface.php
+++ b/src/Adapter/AdapterInterface.php
@@ -11,6 +11,7 @@
 
 namespace Tobyz\JsonApiServer\Adapter;
 
+use Closure;
 use Tobyz\JsonApiServer\Context;
 use Tobyz\JsonApiServer\Schema\Attribute;
 use Tobyz\JsonApiServer\Schema\HasMany;
@@ -226,11 +227,11 @@ interface AdapterInterface
      *
      * @param array $models
      * @param array $relationships
-     * @param mixed $scope Should be called to give the deepest relationship
+     * @param Closure $scope Should be called to give the deepest relationship
      *   an opportunity to scope the query that will fetch related resources
      * @param bool $linkage true if we just need the IDs of the related
      *   resources and not their full data
      * @return mixed
      */
-    public function load(array $models, array $relationships, $scope, bool $linkage): void;
+    public function load(array $models, array $relationships, Closure $scope, bool $linkage): void;
 }
diff --git a/src/Adapter/EloquentAdapter.php b/src/Adapter/EloquentAdapter.php
index be777fa..5958c37 100644
--- a/src/Adapter/EloquentAdapter.php
+++ b/src/Adapter/EloquentAdapter.php
@@ -204,7 +204,7 @@ class EloquentAdapter implements AdapterInterface
         $query->take($limit)->skip($offset);
     }
 
-    public function load(array $models, array $relationships, $scope, bool $linkage): void
+    public function load(array $models, array $relationships, Closure $scope, bool $linkage): void
     {
         // TODO: Find the relation on the model that we're after. If it's a
         // belongs-to relation, and we only need linkage, then we won't need