diff --git a/pyproject.toml b/pyproject.toml
index c008214..c8de05d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,6 +31,7 @@ networkx = ">=2.1"
 numpy = ">=1.20.0"
 rdkit = ">=2022.3.3"
 "ruamel.yaml" = ">0.15"
+PyYAML = ">=6.0"
 scipy = ">=0.1"
 spglib = ">=0.1"
 typer = { version = ">=0.6", extras = ["all"] }