diff --git a/Project.toml b/Project.toml
index d3cb301..fcb3d3d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -18,7 +18,7 @@ FastGaussQuadrature = "0.4.2"
 FastTransforms = "0.11, 0.12, 0.13"
 Parameters = "0.12"
 Requires = "1"
-SpecialFunctions = "1"
+SpecialFunctions = "1, 2"
 julia = "0.7, 1"
 
 [extras]