diff --git a/examples/1-mauna-loa/Project.toml b/examples/1-mauna-loa/Project.toml
index b51c0c81..154704a6 100644
--- a/examples/1-mauna-loa/Project.toml
+++ b/examples/1-mauna-loa/Project.toml
@@ -13,7 +13,7 @@ AbstractGPs = "0.5"
 CSV = "0.9, 0.10"
 DataFrames = "1"
 Literate = "2"
-Optim = "1"
+Optim = "1, 2"
 ParameterHandling = "0.4, 0.5"
 Plots = "1"
 Zygote = "0.6, 0.7"