diff --git a/Creational/Builder/Builder.php b/Creational/Builder/Builder.php
index 6bda440..eadee30 100644
--- a/Creational/Builder/Builder.php
+++ b/Creational/Builder/Builder.php
@@ -8,13 +8,13 @@ use DesignPatterns\Creational\Builder\Parts\Vehicle;
 
 interface Builder
 {
-    public function createVehicle();
+    public function createVehicle(): void;
 
-    public function addWheel();
+    public function addWheel(): void;
 
-    public function addEngine();
+    public function addEngine(): void;
 
-    public function addDoors();
+    public function addDoors(): void;
 
     public function getVehicle(): Vehicle;
 }
diff --git a/Creational/Builder/CarBuilder.php b/Creational/Builder/CarBuilder.php
index b418004..9335a13 100644
--- a/Creational/Builder/CarBuilder.php
+++ b/Creational/Builder/CarBuilder.php
@@ -14,19 +14,19 @@ class CarBuilder implements Builder
 {
     private Car $car;
 
-    public function addDoors()
+    public function addDoors(): void
     {
         $this->car->setPart('rightDoor', new Door());
         $this->car->setPart('leftDoor', new Door());
         $this->car->setPart('trunkLid', new Door());
     }
 
-    public function addEngine()
+    public function addEngine(): void
     {
         $this->car->setPart('engine', new Engine());
     }
 
-    public function addWheel()
+    public function addWheel(): void
     {
         $this->car->setPart('wheelLF', new Wheel());
         $this->car->setPart('wheelRF', new Wheel());
@@ -34,7 +34,7 @@ class CarBuilder implements Builder
         $this->car->setPart('wheelRR', new Wheel());
     }
 
-    public function createVehicle()
+    public function createVehicle(): void
     {
         $this->car = new Car();
     }
diff --git a/Creational/Builder/TruckBuilder.php b/Creational/Builder/TruckBuilder.php
index 2be7f4e..b9d57df 100644
--- a/Creational/Builder/TruckBuilder.php
+++ b/Creational/Builder/TruckBuilder.php
@@ -14,18 +14,18 @@ class TruckBuilder implements Builder
 {
     private Truck $truck;
 
-    public function addDoors()
+    public function addDoors(): void
     {
         $this->truck->setPart('rightDoor', new Door());
         $this->truck->setPart('leftDoor', new Door());
     }
 
-    public function addEngine()
+    public function addEngine(): void
     {
         $this->truck->setPart('truckEngine', new Engine());
     }
 
-    public function addWheel()
+    public function addWheel(): void
     {
         $this->truck->setPart('wheel1', new Wheel());
         $this->truck->setPart('wheel2', new Wheel());
@@ -35,7 +35,7 @@ class TruckBuilder implements Builder
         $this->truck->setPart('wheel6', new Wheel());
     }
 
-    public function createVehicle()
+    public function createVehicle(): void
     {
         $this->truck = new Truck();
     }