diff --git a/setup.py b/setup.py
index 557d4ce..9ff1ed7 100644
--- a/setup.py
+++ b/setup.py
@@ -18,7 +18,7 @@
       ],
       keywords='speech-recognition machine-learning acoustic-models artificial-intelligence neural-networks',
       install_requires=[
-           'nltk==3.4.5',
+           'nltk==3.6.6',
            'numpy>=1.14.5,<2',
            'python-speech-features==0.6',
            'scipy>=1.1.0,<2',