diff --git a/Project.toml b/Project.toml
index 48980c5..44c5caa 100644
--- a/Project.toml
+++ b/Project.toml
@@ -25,7 +25,7 @@ HDF5 = "0.16"
 Interpolations = "0.13"
 LaTeXStrings = "1"
 Optim = "1"
-Polynomials = "3"
+Polynomials = "3, 4"
 QuadGK = "2"
 RecipesBase = "1"
 SpecialFunctions = "2"