diff --git a/src/Container/Container.php b/src/Container/Container.php
index 293297c..076ad1a 100644
--- a/src/Container/Container.php
+++ b/src/Container/Container.php
@@ -58,10 +58,12 @@ public function __construct(bool $shouldBuildContainerMixin = true)
             $this->registerConfiguredProviders();
 
             $this->bootstrap();
-        }
 
-        if ($shouldBuildContainerMixin) {
-            $this->buildContainerMixinManifest();
+            // The mixin describes the registered extensions, so it only needs checking when they are
+            // initialized: checking it on every call costs several filesystem stats per generated value.
+            if ($shouldBuildContainerMixin) {
+                $this->buildContainerMixinManifest();
+            }
         }
     }
 
diff --git a/tests/Unit/ContainerMixinManifestTest.php b/tests/Unit/ContainerMixinManifestTest.php
index 6dce686..6d0dc63 100644
--- a/tests/Unit/ContainerMixinManifestTest.php
+++ b/tests/Unit/ContainerMixinManifestTest.php
@@ -154,4 +154,26 @@ public function testNoExtension()
 
         $this->assertFileExists('/tmp/ContainerMixin.php');
     }
+
+    public function testContainerMixinIsOnlyCheckedWhenExtensionsAreInitialized()
+    {
+        $container = new \Xefi\Faker\Container\Container(shouldBuildContainerMixin: false);
+        $container->forgetExtensions();
+        $container->forgetBootstrappers();
+        @unlink('/tmp/ContainerMixin.php');
+
+        new \Xefi\Faker\Container\Container();
+        $this->assertFileExists('/tmp/ContainerMixin.php');
+
+        unlink('/tmp/ContainerMixin.php');
+        new \Xefi\Faker\Container\Container();
+        $this->assertFileDoesNotExist('/tmp/ContainerMixin.php');
+
+        $container->forgetExtensions();
+        $container->forgetBootstrappers();
+        new \Xefi\Faker\Container\Container();
+        $this->assertFileExists('/tmp/ContainerMixin.php');
+
+        unlink('/tmp/ContainerMixin.php');
+    }
 }