diff --git a/Project.toml b/Project.toml
index 54994aa5..1c7c0954 100644
--- a/Project.toml
+++ b/Project.toml
@@ -30,6 +30,7 @@ AtomBase = "0.1"
 AtomsBase = "0.3"
 AtomsIO = "0.2"
 BenchmarkTools = "1"
+Combinatorics = "1"
 CSV = "0.10"
 DataFrames = "1"
 Distributions = "0.25"