diff --git a/pyproject.toml b/pyproject.toml
index 3b548aa8..77f99fa8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -14,6 +14,9 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "ezc3d"
 dynamic = ["version"]
+dependencies = [
+    "numpy",
+]
 description = "Easy to use C3D reader/writer for C++, Python, and Matlab"
 readme = "README.md"  # This links to your README file
 authors = [