diff --git a/docs/Project.toml b/docs/Project.toml
index c03257c..54cd438 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -23,4 +23,5 @@ Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 
 [compat]
+ForwardDiff = "1.4.1"
 Literate = "2"