diff --git a/crates/fj/src/lib.rs b/crates/fj/src/lib.rs
index 100a9b6b5..294bbb85a 100644
--- a/crates/fj/src/lib.rs
+++ b/crates/fj/src/lib.rs
@@ -40,7 +40,6 @@ use serde::{Deserialize, Serialize};
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[repr(C)]
-#[allow(improper_ctypes)] // Box isn't FFI-safe
 pub enum Shape {
     /// A group of two 3-dimensional shapes
     Group(Box<Group>),