diff --git a/requirements.txt b/requirements.txt
index 83e95bc..99d0614 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-nltk==3.4.5
+nltk==3.9
 numpy==1.14.5
 six==1.11.0
 scikit-learn==0.20.4
diff --git a/setup.py b/setup.py
index 2821dbd..b4ae81c 100644
--- a/setup.py
+++ b/setup.py
@@ -42,7 +42,7 @@
     platforms = "any",
     license='Apache 2.0',
     install_requires=[
-        "nltk == 3.4.5", 
+        "nltk == 3.9", 
         "numpy == 1.14.5",
         "six == 1.11.0",
         "scikit-learn == 0.20.4",