diff --git a/classes/ObjectModel.php b/classes/ObjectModel.php
index 0c70cbf3c..7683055a4 100644
--- a/classes/ObjectModel.php
+++ b/classes/ObjectModel.php
@@ -1234,11 +1234,16 @@ abstract class ObjectModelCore
 		if ($id_shop === null)
 			$id_shop = Context::getContext()->shop->id;
 
-		$sql = 'SELECT id_shop
-				FROM `'.pSQL(_DB_PREFIX_.$this->def['table']).'_shop`
-				WHERE `'.$this->def['primary'].'` = '.(int)$this->id.'
-					AND id_shop = '.(int)$id_shop;
-		return (bool)Db::getInstance()->getValue($sql);
+		$cache_id = 'objectmodel_shop_'.$this->def['classname'].'_'.(int)$this->id.'-'.(int)$id_shop;
+		if (!Cache::isStored($cache_id))
+		{
+			$sql = 'SELECT id_shop
+					FROM `'.pSQL(_DB_PREFIX_.$this->def['table']).'_shop`
+					WHERE `'.$this->def['primary'].'` = '.(int)$this->id.'
+						AND id_shop = '.(int)$id_shop;
+			Cache::store($cache_id, (bool)Db::getInstance()->getValue($sql));
+		}
+		return Cache::retrieve($cache_id);
 	}
 
 	/**
diff --git a/classes/tax/TaxRulesTaxManager.php b/classes/tax/TaxRulesTaxManager.php
index f4fcd87f3..ae6beeb67 100644
--- a/classes/tax/TaxRulesTaxManager.php
+++ b/classes/tax/TaxRulesTaxManager.php
@@ -33,9 +33,6 @@ class TaxRulesTaxManagerCore implements TaxManagerInterface
 	public $type;
 	public $tax_calculator;
 
-	protected static $cache_tax_calculator;
-
-
 	/**
 	 * 
 	 * @param Address $address
@@ -80,8 +77,8 @@ class TaxRulesTaxManagerCore implements TaxManagerInterface
 		if (!empty($this->address->postcode))
 			$postcode = $this->address->postcode;
 
-		$key = (int)$this->address->id_country.'-'.(int)$this->address->id_state.'-'.$postcode.'-'.(int)$this->type;
-		if (!isset(self::$cache_tax_calculator[$key]))
+		$cache_id = (int)$this->address->id_country.'-'.(int)$this->address->id_state.'-'.$postcode.'-'.(int)$this->type;
+		if (!Cache::isStored($cache_id))
 		{
 			$rows = Db::getInstance()->executeS('
 			SELECT *
@@ -111,10 +108,8 @@ class TaxRulesTaxManagerCore implements TaxManagerInterface
 				if ($row['behavior'] == 0)
 					 break;
 			}
-
-			self::$cache_tax_calculator[$key] = new TaxCalculator($taxes, $behavior);
+			Cache::store($cache_id, new TaxCalculator($taxes, $behavior));
 		}
-		return self::$cache_tax_calculator[$key];
+		return Cache::retrieve($cache_id);
 	}
-}
-
+}
\ No newline at end of file