diff --git a/src/DependencyInjection/ExerciseHTMLPurifierExtension.php b/src/DependencyInjection/ExerciseHTMLPurifierExtension.php
index 3383d1c2..f6a5686f 100644
--- a/src/DependencyInjection/ExerciseHTMLPurifierExtension.php
+++ b/src/DependencyInjection/ExerciseHTMLPurifierExtension.php
@@ -27,7 +27,10 @@ public function load(array $configs, ContainerBuilder $container): void
 
         // Set default serializer cache path, while ensuring a default profile is defined
         $configs['html_profiles']['default']['config']['Cache.SerializerPath'] = $configs['default_cache_serializer_path'];
-        $configs['html_profiles']['default']['config']['Cache.SerializerPermissions'] = $configs['default_cache_serializer_permissions'];
+
+        if (!isset($configs['html_profiles']['default']['config']['Cache.SerializerPermissions'])) {
+            $configs['html_profiles']['default']['config']['Cache.SerializerPermissions'] = $configs['default_cache_serializer_permissions'];
+        }
 
         $serializerPaths = [];
         // Drop when require Symfony > 3.4
diff --git a/tests/DependencyInjection/ExerciseHTMLPurifierExtensionTest.php b/tests/DependencyInjection/ExerciseHTMLPurifierExtensionTest.php
index 8a5937f3..fde6d8f8 100644
--- a/tests/DependencyInjection/ExerciseHTMLPurifierExtensionTest.php
+++ b/tests/DependencyInjection/ExerciseHTMLPurifierExtensionTest.php
@@ -153,6 +153,30 @@ public function testShouldAllowOverridingDefaultConfigurationCacheSerializerPerm
         $this->assertRegistryHasProfiles(['default']);
     }
 
+    public function testShouldAllowOverridingDefaultConfigurationCacheSerializerPermissionsOnDefaultProfile(): void
+    {
+        $config = [
+            'default_cache_serializer_path' => null,
+            'html_profiles' => [
+                'default' => [
+                    'config' => [
+                        'AutoFormat.AutoParagraph' => true,
+                        'Cache.SerializerPermissions' => 511,
+                    ],
+                ],
+            ],
+        ];
+
+        $this->extension->load([$config], $this->container);
+
+        $this->assertDefaultConfigDefinition(array_merge($config['html_profiles']['default']['config'], [
+            'Cache.SerializerPath' => null,
+            'Cache.SerializerPermissions' => 511,
+        ]));
+        $this->assertCacheWarmerSerializerArgs([], ['default']);
+        $this->assertRegistryHasProfiles(['default']);
+    }
+
     public function testShouldNotDeepMergeOptions(): void
     {
         $configs = [