diff --git a/pyproject.toml b/pyproject.toml
index be1c2a0..9994a0d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,7 +6,8 @@ build-backend = "setuptools.build_meta"
 # We need at least 1.19.0 for ABI compatibility, but otherwise prefer the oldest available wheel (eg: 1.19.3 for py3.9)
 requires = [
     "numpy==1.19.0; python_version<'3.9'",
-    "oldest-supported-numpy",
+    "numpy==1.19.3; python_version<='3.9'",
+    "numpy==1.19.3; python_version>'3.9'",
     "setuptools",
     "wheel"
 ]