--- a/crates/jrsonnet-ir/src/expr.rs
+++ b/crates/jrsonnet-ir/src/expr.rs
@@ -459,6 +459,7 @@
 	}
 }
 
+#[cfg(target_pointer_width = "64")]
 static_assertions::assert_eq_size!(Span, (usize, usize));
 
 impl Debug for Span {