diff --git a/pyproject.toml b/pyproject.toml
index 8b63d75..e60f27d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ requires = [
     "wheel",
     "setuptools_scm",
     "setuptools_git_ls_files",
-    "cython",
+    "cython<3",
 ]
 
 build-backend = "setuptools.build_meta"