diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..689dda2
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,3 @@
+[build-system]
+requires = ["setuptools", "wheel", "cython", "numpy < 2.0"]
+build-backend = "setuptools.build_meta"
diff --git a/setup.py b/setup.py
index 915beb7..8256c61 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,6 @@
 from setuptools import setup, find_packages, Extension
 import sys
 from pathlib import Path
-import numpy
 
 # with open('README.rst') as readme_file:
 #     readme = readme_file.read()
@@ -30,12 +29,14 @@ def readme():
 
 try:
     from Cython.Build import cythonize
+    import numpy
     extensions = cythonize([
         Extension("fseq2.idr_2_0_3.inv_cdf",
                   ["fseq2/idr_2_0_3/inv_cdf.pyx", ],
                   include_dirs=[numpy.get_include()]),
     ])
 except ImportError:
+    import numpy
     extensions = [
         Extension("fseq2.idr_2_0_3.inv_cdf",
                   ["fseq2/idr_2_0_3/inv_cdf.c", ],