diff --git a/requirements.txt b/requirements.txt
index 90d4c68..6f4e597 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 pydelphin==0.6.0
-nltk==3.6.2
+nltk==3.6.6
 texttaglib>=0.1.1, < 0.2
 yawlib>=0.1, < 0.2
 lelesk>=0.1, < 0.2