diff --git a/docs/Project.toml b/docs/Project.toml
index 5ddd1aa0..325dbf8f 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -12,5 +12,6 @@ Documenter = "1"
 ForwardDiff = "0.10, 1"
 Plots = "1"
 PrettyTables = "3"
+RootedTrees = "2.25.3"
 SymPy = "1, 2"
 Zygote = "0.6, 0.7"