diff --git a/src/Pimple/Container.php b/src/Pimple/Container.php
index 23e851b..3bbd255 100644
--- a/src/Pimple/Container.php
+++ b/src/Pimple/Container.php
@@ -196,7 +196,7 @@ public function protect($callable)
             throw new ExpectedInvokableException('Callable is not a Closure or invokable object.');
         }
 
-        $this->protected->attach($callable);
+        $this->protected->offsetSet($callable);
 
         return $callable;
     }
@@ -268,8 +268,8 @@ public function extend($id, $callable)
         };
 
         if (isset($this->factories[$factory])) {
-            $this->factories->detach($factory);
-            $this->factories->attach($extended);
+            $this->factories->offsetUnset($factory);
+            $this->factories->offsetSet($extended);
         }
 
         return $this[$id] = $extended;