diff --git a/Project.toml b/Project.toml
index dce885f..3bd0cd4 100644
--- a/Project.toml
+++ b/Project.toml
@@ -24,7 +24,7 @@ FITSIO = "0.16, 0.17"
 Interpolations = "0.12, 0.13, 0.14"
 Missings = "0.4.5, 1.0"
 NaNMath = "0.3.5, 1"
-Polynomials = "1.2, 2, 3"
+Polynomials = "1.2, 2, 3, 4"
 Query = "1"
 RvSpectMLBase = "0.2.3"
 StatsBase = "0.33, 0.34"