diff --git a/Project.toml b/Project.toml
index 57bab40..936d5a5 100644
--- a/Project.toml
+++ b/Project.toml
@@ -14,6 +14,7 @@ spglib_jll = "ac4a9f1e-bdb2-5204-990c-47c8b2f70d4e"
 CrystallographyCore = "0.1, 0.2, 0.3"
 StaticArrays = "0.8.3, 0.9, 0.10, 0.11, 0.12, 1.0"
 StructEquality = "1, 2"
+SumTypes = "0.5"
 julia = "1.3"
 spglib_jll = "2"