diff --git a/Project.toml b/Project.toml
index 896f625..d0dfa85 100644
--- a/Project.toml
+++ b/Project.toml
@@ -20,7 +20,7 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [compat]
 ApproxFun = "0.11.8"
-ApproxFunBase = "0.2.3"
+ApproxFunBase = "0.2.3, 0.9"
 ApproxFunFourier = "0.2"
 ApproxFunOrthogonalPolynomials = "0.3"
 ApproxFunSingularities = "0.1.6"