diff --git a/crates/fj-core/src/algorithms/approx/curve/segment.rs b/crates/fj-core/src/algorithms/approx/curve/segment.rs
index 0047e712f..3e8e43932 100644
--- a/crates/fj-core/src/algorithms/approx/curve/segment.rs
+++ b/crates/fj-core/src/algorithms/approx/curve/segment.rs
@@ -70,7 +70,7 @@ impl CurveApproxSegment {
     /// Reduce the approximation to the subset defined by the provided boundary
     pub fn make_subset(&mut self, boundary: CurveBoundary<Point<1>>) {
         assert!(
-            self.boundary.is_normalized(),
+            self.is_normalized(),
             "Expected normalized segment for making subset."
         );
         assert!(