diff --git a/src/pocketmine/item/Bow.php b/src/pocketmine/item/Bow.php
index 4ca73b053..05ff62828 100644
--- a/src/pocketmine/item/Bow.php
+++ b/src/pocketmine/item/Bow.php
@@ -39,7 +39,7 @@ class Bow extends Tool{
 		return 200;
 	}
 
-	public function getMaxDurability(){
+	public function getMaxDurability() : int{
 		return 385;
 	}
 
diff --git a/src/pocketmine/item/Durable.php b/src/pocketmine/item/Durable.php
index d2960f836..f5f67b7e4 100644
--- a/src/pocketmine/item/Durable.php
+++ b/src/pocketmine/item/Durable.php
@@ -82,6 +82,14 @@ abstract class Durable extends Item{
 		return 0;
 	}
 
+
+	/**
+	 * Returns the maximum amount of damage this item can take before it breaks.
+	 *
+	 * @return int
+	 */
+	abstract public function getMaxDurability() : int;
+
 	/**
 	 * Returns whether the item is broken.
 	 * @return bool
diff --git a/src/pocketmine/item/FlintSteel.php b/src/pocketmine/item/FlintSteel.php
index fcce0bf08..4196de9c5 100644
--- a/src/pocketmine/item/FlintSteel.php
+++ b/src/pocketmine/item/FlintSteel.php
@@ -49,7 +49,7 @@ class FlintSteel extends Tool{
 		return false;
 	}
 
-	public function getMaxDurability(){
+	public function getMaxDurability() : int{
 		return 65;
 	}
 }
diff --git a/src/pocketmine/item/Item.php b/src/pocketmine/item/Item.php
index a39fe2b9a..cd4016714 100644
--- a/src/pocketmine/item/Item.php
+++ b/src/pocketmine/item/Item.php
@@ -761,15 +761,6 @@ class Item implements ItemIds, \JsonSerializable{
 		return 0;
 	}
 
-	/**
-	 * Returns the maximum amount of damage this item can take before it breaks.
-	 *
-	 * @return int|bool
-	 */
-	public function getMaxDurability(){
-		return false;
-	}
-
 	public function isPickaxe(){
 		return false;
 	}
diff --git a/src/pocketmine/item/Shears.php b/src/pocketmine/item/Shears.php
index 44129b0d5..3a32b3ab8 100644
--- a/src/pocketmine/item/Shears.php
+++ b/src/pocketmine/item/Shears.php
@@ -30,7 +30,7 @@ class Shears extends Tool{
 		parent::__construct(self::SHEARS, $meta, "Shears");
 	}
 
-	public function getMaxDurability(){
+	public function getMaxDurability() : int{
 		return 239;
 	}
 
diff --git a/src/pocketmine/item/TieredTool.php b/src/pocketmine/item/TieredTool.php
index 4ec1841cd..7fa289889 100644
--- a/src/pocketmine/item/TieredTool.php
+++ b/src/pocketmine/item/TieredTool.php
@@ -38,7 +38,7 @@ abstract class TieredTool extends Tool{
 		$this->tier = $tier;
 	}
 
-	public function getMaxDurability(){
+	public function getMaxDurability() : int{
 		return self::getDurabilityFromTier($this->tier);
 	}