diff --git a/requirements.txt b/requirements.txt
index 0167debe..47f4bb6c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-numpy>=1.21.1
+numpy>=1.21.1,<2
 pandas>=1.3.1
 scipy>=1.8.1
 SALib>=1.4.4