diff --git a/setup.py b/setup.py
index 3dcdfb3..45f620e 100644
--- a/setup.py
+++ b/setup.py
@@ -57,8 +57,10 @@
     install_requires=['pyasn1>=0.3.5',
                       'pyasn1_modules',
                       'javaobj-py3',
-                      'pycryptodomex',
-                      'twofish'],
+                      'pycryptodomex'],
+    extras_require={
+      'twofish': ['twofish'],
+    },
     test_suite="tests.test_jks",
 )