diff --git a/requirements.txt b/requirements.txt
index 152ac433be37ea7ed8900e0a78c9a7fc72f5c189..5da2c627b78219748c05846bc42611628f3d9c1f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -9,3 +9,4 @@ f90nml
 uproot4
 awkward1
 pandas
+mendeleev