diff --git a/src/bin/flat/tube/mod.rs b/src/bin/flat/tube/mod.rs
index 81f06a3..0dee05f 100644
--- a/src/bin/flat/tube/mod.rs
+++ b/src/bin/flat/tube/mod.rs
@@ -190,8 +190,8 @@ mod coords {
 	use super::{Rect, Tube};
 
 	pub trait FlatCoordinateSystem<T> {
-		fn flat_to_global(&self, v: T) -> T { v }
-		fn global_to_flat(&self, v: T) -> T { v }
+		fn flat_to_global(&self, v: T) -> T;
+		fn global_to_flat(&self, v: T) -> T;
 	}
 
 	pub trait FlatRegion: FlatCoordinateSystem<Vec2> + FlatCoordinateSystem<Ray> + FlatCoordinateSystem<Location> {