diff --git a/crates/fj-kernel/src/algorithms/approx/curve.rs b/crates/fj-kernel/src/algorithms/approx/curve.rs
index 45b893d20..aa17fc9b7 100644
--- a/crates/fj-kernel/src/algorithms/approx/curve.rs
+++ b/crates/fj-kernel/src/algorithms/approx/curve.rs
@@ -213,13 +213,12 @@ mod tests {
         let surface = objects
             .surfaces
             .insert(Surface::new(GlobalPath::x_axis(), [0., 0., 1.]))?;
-        let curve = PartialCurve {
+        let mut curve = PartialCurve {
             surface: Some(surface),
             ..Default::default()
-        }
-        .update_as_line_from_points([[1., 1.], [2., 1.]])
-        .build(&objects)?
-        .insert(&objects)?;
+        };
+        curve.update_as_line_from_points([[1., 1.], [2., 1.]]);
+        let curve = curve.build(&objects)?.insert(&objects)?;
         let range = RangeOnPath::from([[0.], [1.]]);
 
         let approx = (&curve, range).approx(1.);
@@ -237,13 +236,12 @@ mod tests {
             GlobalPath::circle_from_radius(1.),
             [0., 0., 1.],
         ))?;
-        let curve = PartialCurve {
+        let mut curve = PartialCurve {
             surface: Some(surface),
             ..Default::default()
-        }
-        .update_as_line_from_points([[1., 1.], [1., 2.]])
-        .build(&objects)?
-        .insert(&objects)?;
+        };
+        curve.update_as_line_from_points([[1., 1.], [1., 2.]]);
+        let curve = curve.build(&objects)?.insert(&objects)?;
         let range = RangeOnPath::from([[0.], [1.]]);
 
         let approx = (&curve, range).approx(1.);
@@ -259,13 +257,12 @@ mod tests {
         let path = GlobalPath::circle_from_radius(1.);
         let surface =
             objects.surfaces.insert(Surface::new(path, [0., 0., 1.]))?;
-        let curve = PartialCurve {
+        let mut curve = PartialCurve {
             surface: Some(surface.clone()),
             ..Default::default()
-        }
-        .update_as_line_from_points([[0., 1.], [1., 1.]])
-        .build(&objects)?
-        .insert(&objects)?;
+        };
+        curve.update_as_line_from_points([[0., 1.], [1., 1.]]);
+        let curve = curve.build(&objects)?.insert(&objects)?;
 
         let range = RangeOnPath::from([[0.], [TAU]]);
         let tolerance = 1.;
diff --git a/crates/fj-kernel/src/algorithms/intersect/curve_face.rs b/crates/fj-kernel/src/algorithms/intersect/curve_face.rs
index c87c06d12..39a74cfa1 100644
--- a/crates/fj-kernel/src/algorithms/intersect/curve_face.rs
+++ b/crates/fj-kernel/src/algorithms/intersect/curve_face.rs
@@ -163,12 +163,12 @@ mod tests {
 
         let surface = objects.surfaces.xy_plane();
 
-        let curve = PartialCurve {
+        let mut curve = PartialCurve {
             surface: Some(surface.clone()),
             ..Default::default()
-        }
-        .update_as_line_from_points([[-3., 0.], [-2., 0.]])
-        .build(&objects)?;
+        };
+        curve.update_as_line_from_points([[-3., 0.], [-2., 0.]]);
+        let curve = curve.build(&objects)?;
 
         #[rustfmt::skip]
         let exterior = [
diff --git a/crates/fj-kernel/src/algorithms/intersect/face_face.rs b/crates/fj-kernel/src/algorithms/intersect/face_face.rs
index d197b5b81..26a992a51 100644
--- a/crates/fj-kernel/src/algorithms/intersect/face_face.rs
+++ b/crates/fj-kernel/src/algorithms/intersect/face_face.rs
@@ -129,13 +129,12 @@ mod tests {
 
         let expected_curves =
             surfaces.try_map_ext(|surface| -> Result<_, ValidationError> {
-                Ok(PartialCurve {
+                let mut curve = PartialCurve {
                     surface: Some(surface),
                     ..Default::default()
-                }
-                .update_as_line_from_points([[0., 0.], [1., 0.]])
-                .build(&objects)?
-                .insert(&objects)?)
+                };
+                curve.update_as_line_from_points([[0., 0.], [1., 0.]]);
+                Ok(curve.build(&objects)?.insert(&objects)?)
             })?;
         let expected_intervals =
             CurveFaceIntersection::from_intervals([[[-1.], [1.]]]);
diff --git a/crates/fj-kernel/src/builder/curve.rs b/crates/fj-kernel/src/builder/curve.rs
index b9e93097b..a16324b32 100644
--- a/crates/fj-kernel/src/builder/curve.rs
+++ b/crates/fj-kernel/src/builder/curve.rs
@@ -15,24 +15,26 @@ pub trait CurveBuilder {
 
     /// Update partial curve as a line, from the provided points
     fn update_as_line_from_points(
-        self,
+        &mut self,
         points: [impl Into<Point<2>>; 2],
-    ) -> Self;
+    ) -> &mut Self;
 }
 
 impl CurveBuilder for PartialCurve {
-    fn update_as_u_axis(self) -> Self {
+    fn update_as_u_axis(mut self) -> Self {
         let a = Point::origin();
         let b = a + Vector::unit_u();
 
-        self.update_as_line_from_points([a, b])
+        self.update_as_line_from_points([a, b]);
+        self
     }
 
-    fn update_as_v_axis(self) -> Self {
+    fn update_as_v_axis(mut self) -> Self {
         let a = Point::origin();
         let b = a + Vector::unit_v();
 
-        self.update_as_line_from_points([a, b])
+        self.update_as_line_from_points([a, b]);
+        self
     }
 
     fn update_as_circle_from_radius(self, radius: impl Into<Scalar>) -> Self {
@@ -43,12 +45,10 @@ impl CurveBuilder for PartialCurve {
     }
 
     fn update_as_line_from_points(
-        self,
+        &mut self,
         points: [impl Into<Point<2>>; 2],
-    ) -> Self {
-        Self {
-            path: Some(SurfacePath::line_from_points(points)),
-            ..self
-        }
+    ) -> &mut Self {
+        self.path = Some(SurfacePath::line_from_points(points));
+        self
     }
 }
diff --git a/crates/fj-kernel/src/builder/cycle.rs b/crates/fj-kernel/src/builder/cycle.rs
index a2499bbd2..64ba97be6 100644
--- a/crates/fj-kernel/src/builder/cycle.rs
+++ b/crates/fj-kernel/src/builder/cycle.rs
@@ -64,11 +64,12 @@ impl CycleBuilder for PartialCycle {
 
                 previous = Some(vertex_next.clone());
 
-                let curve = PartialCurve {
+                let mut curve = PartialCurve {
                     surface: Some(surface.clone()),
                     ..Default::default()
-                }
-                .update_as_line_from_points([position_prev, position_next]);
+                };
+                curve
+                    .update_as_line_from_points([position_prev, position_next]);
 
                 let vertices = [(0., vertex_prev), (1., vertex_next)].map(
                     |(position, surface_form)| {
diff --git a/crates/fj-kernel/src/builder/edge.rs b/crates/fj-kernel/src/builder/edge.rs
index 1c6abd920..c05c65120 100644
--- a/crates/fj-kernel/src/builder/edge.rs
+++ b/crates/fj-kernel/src/builder/edge.rs
@@ -139,12 +139,12 @@ impl HalfEdgeBuilder for PartialHalfEdge {
                 .expect("Can't infer line segment without surface position")
         });
 
-        let curve = PartialCurve {
+        let mut curve = PartialCurve {
             surface: Some(surface),
             global_form: Some(self.extract_global_curve()),
             ..Default::default()
-        }
-        .update_as_line_from_points(points);
+        };
+        curve.update_as_line_from_points(points);
 
         let [back, front] = {
             let vertices = [(from, 0.), (to, 1.)].map(|(vertex, position)| {