diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 3c3b3e5..f3b5181 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -4,7 +4,7 @@ includes:
     - ./vendor/phpstan/phpstan-phpunit/extension.neon
     - ./vendor/phpstan/phpstan-phpunit/rules.neon
 parameters:
-    level: 9
+    level: max
     paths:
         - src
         - tests
diff --git a/src/Relations/BelongsToThrough.php b/src/Relations/BelongsToThrough.php
index 8c6e6d9..c81c9fb 100644
--- a/src/Relations/BelongsToThrough.php
+++ b/src/Relations/BelongsToThrough.php
@@ -32,7 +32,7 @@ class BelongsToThrough extends Relation
     /**
      * The "through" parent model instances.
      *
-     * @var list<\Illuminate\Database\Eloquent\Model>
+     * @var non-empty-list<\Illuminate\Database\Eloquent\Model>
      */
     protected $throughParents;
 
@@ -62,7 +62,7 @@ class BelongsToThrough extends Relation
      *
      * @param \Illuminate\Database\Eloquent\Builder<TRelatedModel> $query
      * @param TDeclaringModel $parent
-     * @param list<\Illuminate\Database\Eloquent\Model> $throughParents
+     * @param non-empty-list<\Illuminate\Database\Eloquent\Model> $throughParents
      * @param string|null $localKey
      * @param string $prefix
      * @param array<string, string> $foreignKeyLookup
@@ -340,10 +340,6 @@ public function getFirstForeignKeyName()
     {
         $firstThroughParent = end($this->throughParents);
 
-        if ($firstThroughParent === false) {
-            throw new RuntimeException('No "through" parent models were specified.'); // @codeCoverageIgnore
-        }
-
         return $this->prefix . $this->getForeignKeyName($firstThroughParent);
     }
 
@@ -356,10 +352,6 @@ public function getQualifiedFirstLocalKeyName()
     {
         $firstThroughParent = end($this->throughParents);
 
-        if ($firstThroughParent === false) {
-            throw new RuntimeException('No "through" parent models were specified.'); // @codeCoverageIgnore
-        }
-
         return $firstThroughParent->qualifyColumn($this->getLocalKeyName($firstThroughParent));
     }
 
diff --git a/src/Traits/BelongsToThrough.php b/src/Traits/BelongsToThrough.php
index 4f9042b..d74848a 100644
--- a/src/Traits/BelongsToThrough.php
+++ b/src/Traits/BelongsToThrough.php
@@ -14,7 +14,7 @@ trait BelongsToThrough
      * @template TRelatedModel of \Illuminate\Database\Eloquent\Model
      *
      * @param class-string<TRelatedModel> $related
-     * @param class-string<\Illuminate\Database\Eloquent\Model>[]|array{0: class-string<\Illuminate\Database\Eloquent\Model>, 1: string}[]|class-string<\Illuminate\Database\Eloquent\Model> $through
+     * @param non-empty-list<class-string<\Illuminate\Database\Eloquent\Model>>|non-empty-list<array{0: class-string<\Illuminate\Database\Eloquent\Model>, 1: string}>|class-string<\Illuminate\Database\Eloquent\Model> $through
      * @param string|null $localKey
      * @param string $prefix
      * @param array<class-string<\Illuminate\Database\Eloquent\Model>, string> $foreignKeyLookup
@@ -124,7 +124,7 @@ protected function belongsToThroughParentInstance($model)
      *
      * @param \Illuminate\Database\Eloquent\Builder<TRelatedModel> $query
      * @param TDeclaringModel $parent
-     * @param list<\Illuminate\Database\Eloquent\Model> $throughParents
+     * @param non-empty-list<\Illuminate\Database\Eloquent\Model> $throughParents
      * @param string|null $localKey
      * @param string $prefix
      * @param array<string, string> $foreignKeyLookup