diff --git a/Cargo.toml b/Cargo.toml
index 59f6b40..3503438 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,7 +5,7 @@ name = "compiler_builtins"
 version = "0.1.0"
 
 [build-dependencies]
-cast = { version = "0.2.0", optional = true }
+cast = { version = "0.2.1", features = ["x128"], optional = true }
 rand = { version = "0.3.15", optional = true }
 
 [build-dependencies.gcc]