diff --git a/requirements/requirements.txt b/requirements/requirements.txt
index f4e3c950..5778f346 100644
--- a/requirements/requirements.txt
+++ b/requirements/requirements.txt
@@ -7,6 +7,7 @@ flask-cors>=3.0.9
 flask-talisman>=0.7.0
 flask-restful>=0.3.9
 networkx>=2.6
+numpy>=1.20.2,<2
 panphon>=0.19
 pyyaml>=5.2
 regex