diff --git a/requirements.txt b/requirements.txt
index 685f830..575dd67 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,5 +2,5 @@ python==3.7
 transformers==4.2.2
 pytorch==1.7.1
 amrlib==0.5.0
-nltk==3.5
+nltk==3.6.6
 scipy==1.6.3