diff --git a/src/politeness3/requirements.txt b/src/politeness3/requirements.txt
index 5b50010..8102190 100644
--- a/src/politeness3/requirements.txt
+++ b/src/politeness3/requirements.txt
@@ -1,5 +1,5 @@
 scipy==0.18.1
 scikit-learn==0.18.1
 numpy==1.21.0
-nltk==3.4.5
+nltk==3.6.6
 requests