diff --git a/setup.py b/setup.py
index ef04b1a8..7e967909 100644
--- a/setup.py
+++ b/setup.py
@@ -63,7 +63,7 @@ def get_version(rel_path):
         "pyjnius==1.2.1",
         "pymagnitude==0.1.143",
         "h5py==2.10.0",
-        "nltk==3.4.5",
+        "nltk==3.6.6",
         "pytest-mock",
         "mock",
         "pyserini==0.13.0",