diff --git a/setup.py b/setup.py
index 3959d8f..d699c05 100644
--- a/setup.py
+++ b/setup.py
@@ -17,7 +17,7 @@
     url='https://github.com/MineralsCloud/cij/',
     packages=find_packages(),
     install_requires=[
-        "numpy >= 1.10.0",
+        "numpy >= 1.10.0, <= 1.21",
         "pandas",
         "scipy",
         "qha",