diff --git a/src/implementations/pointers.rs b/src/implementations/pointers.rs
index fe9a0b2..c7f5e82 100644
--- a/src/implementations/pointers.rs
+++ b/src/implementations/pointers.rs
@@ -4,7 +4,10 @@ use core::{
     mem::ManuallyDrop,
 };
 
+// Box is only available with alloc.
+#[cfg(feature = "std")]
 impl_new_from_pseudo_default!(Box<T>, T);
+
 impl_new_from_pseudo_default!(UnsafeCell<T>, T);
 impl_new_from_pseudo_default!(RefCell<T>, T);
 impl_new_from_pseudo_default!(ManuallyDrop<T>, T);