diff --git a/.gitignore b/.gitignore
index 2c8de41..5c3be21 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 /vendor/
 /node_modules/
 composer.lock
+.phpunit.cache/
\ No newline at end of file
diff --git a/composer.json b/composer.json
index 0164688..a770f21 100644
--- a/composer.json
+++ b/composer.json
@@ -2,6 +2,16 @@
     "name": "sofa/eloquence-mappable",
     "description": "Flexible Searchable, Mappable, Metable, Validation and more extensions for Laravel Eloquent ORM.",
     "license": "MIT",
+    "repositories": [
+        {
+            "type": "vcs",
+            "url": "https://github.com/erasys/eloquence-base"
+        },
+        {
+            "type": "vcs",
+            "url": "https://github.com/erasys/hookable"
+        }
+    ],
     "support": {
         "issues": "https://github.com/jarektkaczyk/eloquence-mappable/issues",
         "source": "https://github.com/jarektkaczyk/eloquence-mappable"
@@ -33,14 +43,14 @@
       }
     ],
     "require": {
-        "php": ">=7.1.0",
-        "sofa/eloquence-base": "dev-7.1.2-erasys as 7.1.2"
+        "php": ">=8.2",
+        "sofa/eloquence-base": "8.0.1"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.5",
-        "squizlabs/php_codesniffer": "2.3.3",
-        "mockery/mockery": "^1.0",
-        "friendsofphp/php-cs-fixer": "^2.0"
+        "squizlabs/php_codesniffer": "^3.7",
+        "mockery/mockery": "^1.5",
+        "friendsofphp/php-cs-fixer": "^3.18.0"
     },
     "autoload": {
         "psr-4": {
@@ -55,7 +65,7 @@
     "minimum-stability": "dev",
     "prefer_stable": true,
     "scripts": {
-        "test": "phpunit && ./vendor/bin/phpcs src --standard=psr2 --report=diff --colors",
+        "test": "./vendor/bin/phpunit && ./vendor/bin/phpcs src --standard=psr2 --report=diff --colors",
         "phpcs": "./vendor/bin/phpcs src --standard=psr2 --report=diff --colors"
     }
 }
diff --git a/src/Mappable.php b/src/Mappable.php
index bbc5c7b..e4f9708 100644
--- a/src/Mappable.php
+++ b/src/Mappable.php
@@ -40,7 +40,7 @@ trait Mappable
      *
      * @return void
      */
-    public static function bootMappable()
+    public static function bootMappable() : void
     {
         $hooks = new Hooks;
 
@@ -64,7 +64,7 @@ public static function bootMappable()
      * @param  \Sofa\Hookable\Contracts\ArgumentBag $args
      * @return mixed
      */
-    protected function mappedQuery(Builder $query, $method, ArgumentBag $args)
+    protected function mappedQuery(Builder $query, $method, ArgumentBag $args) : mixed
     {
         $mapping = $this->getMappingForAttribute($args->get('column'));
 
@@ -107,7 +107,7 @@ protected function mappedGroupBy(Builder $query, ArgumentBag $args)
      * @param  \Sofa\Hookable\Contracts\ArgumentBag $args
      * @return void
      */
-    protected function mappedSelect(Builder $query, ArgumentBag $args)
+    protected function mappedSelect(Builder $query, ArgumentBag $args) : void
     {
         $columns = $args->get('columns');
 
@@ -154,7 +154,7 @@ protected function mappedSelect(Builder $query, ArgumentBag $args)
      * @param  string $mapping
      * @return mixed
      */
-    protected function mappedRelationQuery($query, $method, ArgumentBag $args, $mapping)
+    protected function mappedRelationQuery($query, $method, ArgumentBag $args, $mapping) : mixed
     {
         list($target, $column) = $this->parseMappedColumn($mapping);
 
@@ -162,6 +162,10 @@ protected function mappedRelationQuery($query, $method, ArgumentBag $args, $mapp
             return $this->mappedJoinQuery($query, $method, $args, $target, $column);
         }
 
+        if (in_array($method, ['whereNull', 'whereNotNull'])) {
+            return $this->mappedWhereQuery($query, $method, $args, $target, $column);
+        }
+
         return $this->mappedHasQuery($query, $method, $args, $target, $column);
     }
 
@@ -175,7 +179,7 @@ protected function mappedRelationQuery($query, $method, ArgumentBag $args, $mapp
      * @param  string $column
      * @return mixed
      */
-    protected function mappedJoinQuery($query, $method, ArgumentBag $args, $target, $column)
+    protected function mappedJoinQuery($query, $method, ArgumentBag $args, $target, $column) : mixed
     {
         $table = $this->joinMapped($query, $target);
 
@@ -198,7 +202,7 @@ protected function mappedJoinQuery($query, $method, ArgumentBag $args, $target,
      * @param  string $target
      * @return \Sofa\Eloquence\Builder
      */
-    protected function orderByMapped(Builder $query, ArgumentBag $args, $table, $column, $target)
+    protected function orderByMapped(Builder $query, ArgumentBag $args, $table, $column, $target) : Builder
     {
         $query->with($target)->getQuery()->orderBy("{$table}.{$column}", $args->get('direction'));
 
@@ -213,7 +217,7 @@ protected function orderByMapped(Builder $query, ArgumentBag $args, $table, $col
      *
      * @return array
      */
-    protected function listsMapped(Builder $query, ArgumentBag $args, $table, $column)
+    protected function listsMapped(Builder $query, ArgumentBag $args, $table, $column) : array
     {
         return $this->pluckMapped($query, $args, $table, $column);
     }
@@ -225,9 +229,9 @@ protected function listsMapped(Builder $query, ArgumentBag $args, $table, $colum
      * @param  \Sofa\Hookable\Contracts\ArgumentBag $args
      * @param  string $table
      * @param  string $column
-     * @return array
+     * @return mixed
      */
-    protected function pluckMapped(Builder $query, ArgumentBag $args, $table, $column)
+    protected function pluckMapped(Builder $query, ArgumentBag $args, $table, $column) : mixed
     {
         $query->select("{$table}.{$column}");
 
@@ -247,7 +251,7 @@ protected function pluckMapped(Builder $query, ArgumentBag $args, $table, $colum
      * @param  string $key
      * @return \Sofa\Eloquence\Builder
      */
-    protected function mappedSelectListsKey(Builder $query, $key)
+    protected function mappedSelectListsKey(Builder $query, $key) : Builder
     {
         if ($this->hasColumn($key)) {
             return $query->addSelect($this->getTable() . '.' . $key);
@@ -263,7 +267,7 @@ protected function mappedSelectListsKey(Builder $query, $key)
      * @param  string $target
      * @return string
      */
-    protected function joinMapped(Builder $query, $target)
+    protected function joinMapped(Builder $query, $target) : string
     {
         $query->prefixColumnsForJoin();
 
@@ -284,7 +288,7 @@ protected function joinMapped(Builder $query, $target)
      * @param  \Illuminate\Database\Eloquent\Model $parent
      * @return array
      */
-    protected function joinSegment(Builder $query, $segment, EloquentModel $parent)
+    protected function joinSegment(Builder $query, $segment, EloquentModel $parent) : array
     {
         $relation = $parent->{$segment}();
         $related = $relation->getRelated();
@@ -319,7 +323,7 @@ protected function joinSegment(Builder $query, $segment, EloquentModel $parent)
      * @param  string  $table
      * @return bool
      */
-    protected function alreadyJoined(Builder $query, $table)
+    protected function alreadyJoined(Builder $query, $table) : bool
     {
         $joined = Arr::pluck((array) $query->getQuery()->joins, 'table');
 
@@ -334,7 +338,7 @@ protected function alreadyJoined(Builder $query, $table)
      *
      * @throws \LogicException
      */
-    protected function getJoinKeys(Relation $relation)
+    protected function getJoinKeys(Relation $relation) : array
     {
         if ($relation instanceof HasOne || $relation instanceof MorphOne) {
             return [$relation->getQualifiedForeignKeyName(), $relation->getQualifiedParentKeyName()];
@@ -359,7 +363,7 @@ protected function getJoinKeys(Relation $relation)
      * @param  string $qualifiedColumn
      * @return mixed
      */
-    protected function mappedSingleResult(Builder $query, $method, $qualifiedColumn)
+    protected function mappedSingleResult(Builder $query, $method, $qualifiedColumn) : mixed
     {
         return $query->getQuery()->select("{$qualifiedColumn}")->{$method}("{$qualifiedColumn}");
     }
@@ -374,7 +378,7 @@ protected function mappedSingleResult(Builder $query, $method, $qualifiedColumn)
      * @param  string $column
      * @return \Sofa\Eloquence\Builder
      */
-    protected function mappedHasQuery(Builder $query, $method, ArgumentBag $args, $target, $column)
+    protected function mappedHasQuery(Builder $query, $method, ArgumentBag $args, $target, $column) : Builder
     {
         $boolean = $this->getMappedBoolean($args);
 
@@ -386,6 +390,28 @@ protected function mappedHasQuery(Builder $query, $method, ArgumentBag $args, $t
             ->has($target, $operator, 1, $boolean, $this->getMappedWhereConstraint($method, $args))
             ->with($target);
     }
+    /**
+     * Add whereNull/WhereNotNull subquery on the mapped attribute relation.
+     *
+     * @param  \Sofa\Eloquence\Builder $query
+     * @param  string $method
+     * @param  \Sofa\Hookable\Contracts\ArgumentBag $args
+     * @param  string $target
+     * @param  string $column
+     * @return \Sofa\Eloquence\Builder
+     */
+    protected function mappedWhereQuery(Builder $query, $method, ArgumentBag $args, $target, $column) : Builder
+    {
+        $boolean = $this->getMappedBoolean($args);
+        $operator = $this->getMappedOperator($method, $args);
+
+        $args->set('columns', $column);
+        $args->unset('column');
+
+        return $query
+            ->has($target, $operator, 1, $boolean, $this->getMappedWhereConstraint($method, $args))
+            ->with($target);
+    }
 
     /**
      * Get the relation constraint closure.
@@ -394,7 +420,7 @@ protected function mappedHasQuery(Builder $query, $method, ArgumentBag $args, $t
      * @param  \Sofa\Hookable\Contracts\ArgumentBag $args
      * @return \Closure
      */
-    protected function getMappedWhereConstraint($method, ArgumentBag $args)
+    protected function getMappedWhereConstraint($method, ArgumentBag $args) : \Closure
     {
         return function ($query) use ($method, $args) {
             call_user_func_array([$query, $method], $args->all());
@@ -407,7 +433,7 @@ protected function getMappedWhereConstraint($method, ArgumentBag $args)
      * @param  \Sofa\EloquenceArgumentBag $args
      * @return string
      */
-    protected function getMappedBoolean(ArgumentBag $args)
+    protected function getMappedBoolean(ArgumentBag $args) : string
     {
         $boolean = $args->get('boolean');
 
@@ -423,7 +449,7 @@ protected function getMappedBoolean(ArgumentBag $args)
      * @param  \Sofa\Hookable\Contracts\ArgumentBag $args
      * @return string
      */
-    protected function getMappedOperator($method, ArgumentBag $args)
+    protected function getMappedOperator($method, ArgumentBag $args) : string
     {
         if ($not = $args->get('not')) {
             $args->set('not', false);
@@ -442,11 +468,12 @@ protected function getMappedOperator($method, ArgumentBag $args)
      * @param  string $key
      * @return string|null
      */
-    public function getMappingForAttribute($key)
+    public function getMappingForAttribute($key) : ?string
     {
         if ($this->hasMapping($key)) {
             return $this->mappedAttributes[$key];
         }
+        return null;
     }
 
     /**
@@ -455,9 +482,9 @@ public function getMappingForAttribute($key)
      * @param  string $mapping
      * @return bool
      */
-    protected function relationMapping($mapping)
+    protected function relationMapping($mapping) : bool
     {
-        return strpos($mapping, '.') !== false;
+        return strpos((string)$mapping, '.') !== false;
     }
 
     /**
@@ -466,7 +493,7 @@ protected function relationMapping($mapping)
      * @param  string $key
      * @return bool
      */
-    public function hasMapping($key)
+    public function hasMapping($key) : bool
     {
         if (is_null($this->mappedAttributes)) {
             $this->parseMappings();
@@ -480,7 +507,7 @@ public function hasMapping($key)
      *
      * @return void
      */
-    protected function parseMappings()
+    protected function parseMappings() : void
     {
         $this->mappedAttributes = [];
 
@@ -500,7 +527,7 @@ protected function parseMappings()
      * @param  string $target
      * @return void
      */
-    protected function parseImplicitMapping($attributes, $target)
+    protected function parseImplicitMapping($attributes, $target) : void
     {
         foreach ($attributes as $attribute) {
             $this->mappedAttributes[$attribute] = "{$target}.{$attribute}";
@@ -513,7 +540,7 @@ protected function parseImplicitMapping($attributes, $target)
      * @param  string $key
      * @return mixed
      */
-    protected function mapAttribute($key)
+    protected function mapAttribute($key) : mixed
     {
         $segments = explode('.', $this->getMappingForAttribute($key));
 
@@ -527,11 +554,11 @@ protected function mapAttribute($key)
      * @param  array  $segments
      * @return mixed
      */
-    protected function getTarget($target, array $segments)
+    protected function getTarget($target, array $segments) : mixed
     {
         foreach ($segments as $segment) {
             if (!$target) {
-                return;
+                return null;
             }
 
             $target = $target->{$segment};
@@ -546,7 +573,7 @@ protected function getTarget($target, array $segments)
      * @param string $key
      * @param mixed  $value
      */
-    protected function setMappedAttribute($key, $value)
+    protected function setMappedAttribute($key, $value) : void
     {
         $segments = explode('.', $this->getMappingForAttribute($key));
 
@@ -564,7 +591,7 @@ protected function setMappedAttribute($key, $value)
      *
      * @param \Illuminate\Database\Eloquent\Model $target
      */
-    protected function addTargetToSave($target)
+    protected function addTargetToSave($target) : void
     {
         if ($this !== $target) {
             $this->targetsToSave[] = $target;
@@ -576,7 +603,7 @@ protected function addTargetToSave($target)
      *
      * @return void
      */
-    protected function saveMapped()
+    protected function saveMapped() : void
     {
         foreach (array_unique($this->targetsToSave) as $target) {
             $target->save();
@@ -591,7 +618,7 @@ protected function saveMapped()
      * @param  string $key
      * @return void
      */
-    protected function forget($key)
+    protected function forget($key) : void
     {
         $mapping = $this->getMappingForAttribute($key);
 
@@ -610,7 +637,7 @@ protected function forget($key)
      *
      * @inheritdoc
      */
-    protected function mutateAttributeForArray($key, $value)
+    protected function mutateAttributeForArray($key, $value) : mixed
     {
         if ($this->hasMapping($key)) {
             $value = $this->mapAttribute($key);
@@ -626,7 +653,7 @@ protected function mutateAttributeForArray($key, $value)
      *
      * @return array
      */
-    public function getMaps()
+    public function getMaps() : array
     {
         return (property_exists($this, 'maps')) ? $this->maps : [];
     }
diff --git a/tests/MappableTest.php b/tests/MappableTest.php
index 6294112..1803108 100644
--- a/tests/MappableTest.php
+++ b/tests/MappableTest.php
@@ -403,6 +403,10 @@ class MappableStub
         saveMapped         as protectedSaveMapped;
     }
 
+    public $bar;
+    
+    public $related;
+
     protected $maps = [
         // local alias
         'alias' => 'original',        // $this->original