diff --git a/requirements.txt b/requirements.txt
index 04e9709..c36ec3d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -85,7 +85,7 @@ mxnet-cu90==1.6.0.post0
 nbconvert==5.4.0
 nbformat==4.4.0
 networkx==2.4
-nltk==3.3
+nltk==3.6.3
 notebook==5.7.0
 numba==0.45.1
 numpy==1.18.5