diff --git a/crates/fj-core/src/operations/build/cycle.rs b/crates/fj-core/src/operations/build/cycle.rs
index 5195766d0..7a6cc46c6 100644
--- a/crates/fj-core/src/operations/build/cycle.rs
+++ b/crates/fj-core/src/operations/build/cycle.rs
@@ -59,7 +59,9 @@ pub trait BuildCycle {
             [[a, b], [b, c], [c, d], [d, a]]
                 .into_iter()
                 .map(|[start, end]| {
-                    HalfEdge::arc(start, end, angle, surface.clone(), core)
+                    let (half_edge, _) =
+                        HalfEdge::arc(start, end, angle, surface.clone(), core);
+                    half_edge
                 });
 
         Cycle::new(half_edges)
diff --git a/crates/fj-core/src/operations/build/half_edge.rs b/crates/fj-core/src/operations/build/half_edge.rs
index f33791f53..45202e88b 100644
--- a/crates/fj-core/src/operations/build/half_edge.rs
+++ b/crates/fj-core/src/operations/build/half_edge.rs
@@ -50,7 +50,7 @@ pub trait BuildHalfEdge {
         angle_rad: impl Into<Scalar>,
         surface: Handle<Surface>,
         core: &mut Core,
-    ) -> Handle<HalfEdge> {
+    ) -> (Handle<HalfEdge>, CurveBoundary<Point<1>>) {
         let angle_rad = angle_rad.into();
         if angle_rad <= -Scalar::TAU || angle_rad >= Scalar::TAU {
             panic!("arc angle must be in the range (-2pi, 2pi) radians");
@@ -76,7 +76,7 @@ pub trait BuildHalfEdge {
             .geometry
             .define_half_edge(half_edge.clone(), HalfEdgeGeom { boundary });
 
-        half_edge
+        (half_edge, boundary)
     }
 
     /// Create a line segment