diff --git a/Project.toml b/Project.toml
index 6606bc2..d9e2993 100644
--- a/Project.toml
+++ b/Project.toml
@@ -23,7 +23,7 @@ CovSel = "0.2"
 Ipopt = "1"
 JuMP = "1"
 LinearAlgebra = "1"
-ProximalBase = "0.3.2"
+ProximalBase = "0.3.2, 0.4"
 Random = "1"
 SparseArrays = "1"
 SpecialFunctions = "2"