diff --git a/Project.toml b/Project.toml
index 7ca2e9ce..b1e172b6 100644
--- a/Project.toml
+++ b/Project.toml
@@ -82,7 +82,7 @@ SparseDiffTools = "0.10, 1.0"
 SparsityDetection = "0.1, 0.2"
 StaticArrays = "0.10, 0.11, 0.12"
 StatsPlots = "0.12, 0.13, 0.14"
-Sundials = "3.8"
+Sundials = "3.8, 4.0"
 Unitful = "0.17, 0.18, 1.0"
 Weave = "0.9"
 julia = "1"