diff --git a/src/Symfony/Component/Config/ResourceCheckerConfigCache.php b/src/Symfony/Component/Config/ResourceCheckerConfigCache.php
index 421db6408a..ab8c99eead 100644
--- a/src/Symfony/Component/Config/ResourceCheckerConfigCache.php
+++ b/src/Symfony/Component/Config/ResourceCheckerConfigCache.php
@@ -132,6 +132,10 @@ class ResourceCheckerConfigCache implements ConfigCacheInterface
                 // discard chmod failure (some filesystem may not support it)
             }
         }
+
+        if (\function_exists('opcache_invalidate') && ini_get('opcache.enable')) {
+            @opcache_invalidate($this->file, true);
+        }
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/Container.php b/src/Symfony/Component/DependencyInjection/Container.php
index 75ba8a2bdb..88f2ce5cf8 100644
--- a/src/Symfony/Component/DependencyInjection/Container.php
+++ b/src/Symfony/Component/DependencyInjection/Container.php
@@ -183,6 +183,7 @@ class Container implements ResettableContainerInterface
             unset($this->aliases[$id]);
         }
 
+        $wasSet = isset($this->services[$id]);
         $this->services[$id] = $service;
 
         if (null === $service) {
@@ -196,11 +197,11 @@ class Container implements ResettableContainerInterface
             } else {
                 @trigger_error(sprintf('Setting the "%s" private service is deprecated since Symfony 3.2 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
             }
-        } elseif (isset($this->fileMap[$id]) || isset($this->methodMap[$id])) {
+        } elseif ($wasSet && (isset($this->fileMap[$id]) || isset($this->methodMap[$id]))) {
             if (null === $service) {
-                @trigger_error(sprintf('Unsetting the "%s" pre-defined service is deprecated since Symfony 3.3 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('Unsetting the "%s" service after it\'s been initialized is deprecated since Symfony 3.3 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
             } else {
-                @trigger_error(sprintf('Setting the "%s" pre-defined service is deprecated since Symfony 3.3 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('Setting the "%s" service after it\'s been initialized is deprecated since Symfony 3.3 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
             }
         }
     }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
index d49df4ec42..ad696482a5 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
@@ -196,15 +196,29 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Unsetting the "bar" pre-defined service is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation Unsetting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
      */
-    public function testSetWithNullResetPredefinedService()
+    public function testSetWithNullOnInitializedPredefinedService()
     {
         $sc = new Container();
         $sc->set('foo', new \stdClass());
         $sc->set('foo', null);
         $this->assertFalse($sc->has('foo'), '->set() with null service resets the service');
 
+        $sc = new ProjectServiceContainer();
+        $sc->get('bar');
+        $sc->set('bar', null);
+        $this->assertTrue($sc->has('bar'), '->set() with null service resets the pre-defined service');
+    }
+
+    public function testSetWithNullOnUninitializedPredefinedService()
+    {
+        $sc = new Container();
+        $sc->set('foo', new \stdClass());
+        $sc->get('foo', null);
+        $sc->set('foo', null);
+        $this->assertFalse($sc->has('foo'), '->set() with null service resets the service');
+
         $sc = new ProjectServiceContainer();
         $sc->set('bar', null);
         $this->assertTrue($sc->has('bar'), '->set() with null service resets the pre-defined service');
@@ -502,7 +516,7 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Setting the "bar" pre-defined service is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation Setting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
      */
     public function testReplacingAPreDefinedServiceIsDeprecated()
     {
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
index f4c25cd9d2..37e5cc451a 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
@@ -287,7 +287,7 @@ class PhpDumperTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Setting the "bar" pre-defined service is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation Setting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
      */
     public function testOverrideServiceWhenUsingADumpedContainer()
     {
@@ -295,15 +295,16 @@ class PhpDumperTest extends TestCase
         require_once self::$fixturesPath.'/includes/foo.php';
 
         $container = new \ProjectServiceContainer();
-        $container->set('bar', $bar = new \stdClass());
         $container->setParameter('foo_bar', 'foo_bar');
+        $container->get('bar');
+        $container->set('bar', $bar = new \stdClass());
 
         $this->assertSame($bar, $container->get('bar'), '->set() overrides an already defined service');
     }
 
     /**
      * @group legacy
-     * @expectedDeprecation Setting the "bar" pre-defined service is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation Setting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
      */
     public function testOverrideServiceWhenUsingADumpedContainerAndServiceIsUsedFromAnotherOne()
     {
@@ -312,6 +313,8 @@ class PhpDumperTest extends TestCase
         require_once self::$fixturesPath.'/includes/classes.php';
 
         $container = new \ProjectServiceContainer();
+        $container->setParameter('foo_bar', 'foo_bar');
+        $container->get('bar');
         $container->set('bar', $bar = new \stdClass());
 
         $this->assertSame($bar, $container->get('foo')->bar, '->set() overrides an already defined service');