diff --git a/dev-requirements.txt b/dev-requirements.txt
index 9ff9529e3..2035d46d1 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -98,7 +98,7 @@ mypy-extensions==1.0.0
     # via mypy
 nodeenv==1.9.1
     # via pre-commit
-numpy==2.1.1
+numpy==1.26.4
     # via
     #   pynxtools (pyproject.toml)
     #   ase
diff --git a/pyproject.toml b/pyproject.toml
index 8dc2e354a..b2b22876d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -28,7 +28,7 @@ dependencies = [
     "h5py>=3.6.0",
     "xarray>=0.20.2",
     "PyYAML>=6.0",
-    "numpy>=1.21.2",
+    'numpy>=1.22.4,<2.0.0',
     "pandas>=1.3.2",
     "ase>=3.19.0",
     "mergedeep",