diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 8c72c5e..dc041fc 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -3,7 +3,7 @@ name: tests
 on: [push]
 
 jobs:
-  tests:
+  no_ext_tests:
     runs-on: ubuntu-22.04
 
     strategy:
@@ -27,5 +27,5 @@ jobs:
           configuration: tests/phpunit.xml
           version: 10.5
           php_version: ${{ matrix.php }}
-          php_extensions: ffi
+          args: --filter ReleaseTest
 
diff --git a/src/BufferFactory.php b/src/BufferFactory.php
index 762471f..891167b 100644
--- a/src/BufferFactory.php
+++ b/src/BufferFactory.php
@@ -7,7 +7,7 @@ class BufferFactory
 {
     public function isAvailable() : bool
     {
-        return extension_loaded('ffi');
+        return class_exists(FFI::class);
     }
 
     public function Buffer(int $size, int $dtype) : Buffer
diff --git a/tests/RindowTest/Math/Matrix/Buffer/FFI/ReleaseTest.php b/tests/RindowTest/Math/Matrix/Buffer/FFI/ReleaseTest.php
new file mode 100644
index 0000000..1e6cebe
--- /dev/null
+++ b/tests/RindowTest/Math/Matrix/Buffer/FFI/ReleaseTest.php
@@ -0,0 +1,22 @@
+<?php
+namespace RindowTest\Math\Buffer\FFI\ReleaseTest;
+
+use PHPUnit\Framework\TestCase;
+use Rindow\Math\Buffer\FFI\BufferFactory;
+use Rindow\Math\Buffer\FFI\Buffer;
+use Interop\Polite\Math\Matrix\NDArray;
+use FFI;
+
+class ReleaseTest extends TestCase
+{
+    public function testFFINotLoaded()
+    {
+        $factory = new BufferFactory();
+        if(extension_loaded('ffi')) {
+            $buffer = $factory->Buffer(1,NDArray::float32);
+            $this->assertInstanceof(Buffer::class,$buffer);
+        } else {
+            $this->assertFalse($factory->isAvailable());
+        }
+    }
+}
\ No newline at end of file