diff --git a/pyproject.toml b/pyproject.toml
index 2d8b1eb..8a239d4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -20,6 +20,6 @@ Homepage = "https://git.aquila-consortium.org/guilhem_lavaux/pysphereproj"
 Issues = "https://git.aquila-consortium.org/guilhem_lavaux/pysphereproj/issues"
 
 [build-system]
-requires = ["setuptools >= 61.0", "wheel", "Cython"]
+requires = ["setuptools >= 61.0", "numpy", "wheel", "Cython"]
 build-backend = "setuptools.build_meta"
 
diff --git a/setup.py b/setup.py
index 29f97fd..f68ed16 100644
--- a/setup.py
+++ b/setup.py
@@ -1,5 +1,6 @@
 from setuptools import setup, Extension
 from Cython.Build import cythonize
+import numpy
 
 extensions = [
     Extension(
@@ -7,7 +8,7 @@ extensions = [
         sources=[
             "ext_src/_project.pyx"
         ],
-        include_dirs=["ext_src"],
+        include_dirs=["ext_src", numpy.get_include()],
         language="c++"
     )
 ]