diff --git a/main/Base/Hstore.class.php b/main/Base/Hstore.class.php
index 84238beed2..f49440cf3e 100644
--- a/main/Base/Hstore.class.php
+++ b/main/Base/Hstore.class.php
@@ -85,7 +85,7 @@ public function drop($key)
 		
 		public function isExists($key)
 		{
-			return isset($this->properties[$key]);
+			return key_exists($key, $this->properties);
 		}
 		
 		/**
diff --git a/test/main/HstoreTest.class.php b/test/main/HstoreTest.class.php
index 8938d868a4..3b8226a4fa 100644
--- a/test/main/HstoreTest.class.php
+++ b/test/main/HstoreTest.class.php
@@ -16,11 +16,15 @@ public function testRun()
 			$array = array(
 				'1' => 'qqer',
 				'f' => 'qs34$9&)_@+#qer',
+				'null' => null
 			);
 
 			$test = Hstore::make($array);
 			$test2= Hstore::create($test->toString());
 
 			$this->assertEquals($test->toString(), $test2->toString());
+
+			$this->assertTrue($test->isExists('null'));
+			$this->assertFalse($test->isExists('notExist'));
 		}
 	}