diff --git a/crates/geom/src/path.rs b/crates/geom/src/path.rs
index 4455c4ed9..d836d2e02 100644
--- a/crates/geom/src/path.rs
+++ b/crates/geom/src/path.rs
@@ -278,7 +278,7 @@ impl SubPath {
         }
         let mut pos = vec![0.0];
         for i in 0..self.segment_count() {
-            let len = kurbo::ParamCurveArclen::arclen(&self.segment(i), 1e-3);
+            let len = measured_arclen(&PathSeg::Cubic(self.segment(i)), 1e-3);
             pos.push(pos.last().copied().unwrap_or(0.0) + len);
         }
         pos
@@ -621,7 +621,7 @@ const MEASURE_LIMIT: f64 = 1e9;
 
 /// The length of `seg` to `accuracy`; 0 for a segment whose control points are not finite or past
 /// [`MEASURE_LIMIT`].
-pub(crate) fn measured_arclen(seg: &PathSeg, accuracy: f64) -> f64 {
+pub fn measured_arclen(seg: &PathSeg, accuracy: f64) -> f64 {
     let ok = |p: Point| p.x.is_finite() && p.y.is_finite() && p.x.abs() <= MEASURE_LIMIT && p.y.abs() <= MEASURE_LIMIT;
     let fits = match seg {
         PathSeg::Line(l) => ok(l.p0) && ok(l.p1),
@@ -838,6 +838,13 @@ mod tests {
         assert_eq!(c.kind, AnchorKind::Corner);
     }
 
+    /// Handles too large to measure give the curve no length instead of subdividing it without end.
+    #[test]
+    fn anchor_positions_of_an_unmeasurable_curve_are_finite() {
+        let p = curve(Point::new(100.0, 1e300), Point::new(300.0, -1e300));
+        assert_eq!(p.subpaths[0].anchor_arc_positions(), [0.0, 0.0]);
+    }
+
     #[test]
     fn length_of_square() {
         assert!((square().length() - 40.0).abs() < 1e-6);
diff --git a/crates/pathops/src/edit.rs b/crates/pathops/src/edit.rs
index 32b47b7b9..2a39cccfa 100644
--- a/crates/pathops/src/edit.rs
+++ b/crates/pathops/src/edit.rs
@@ -3,7 +3,8 @@
 
 use std::collections::{BTreeMap, BTreeSet};
 
-use kurbo::{CubicBez, ParamCurveArclen, Point, Rect, Vec2};
+use kurbo::{CubicBez, PathSeg, Point, Rect, Vec2};
+use vectorcraft_geom::path::measured_arclen;
 use vectorcraft_geom::{Anchor, AnchorKind, PathData, SubPath};
 
 use crate::boolean::{Seg, segs_to_subpath};
@@ -115,7 +116,8 @@ fn simplify_run(run: &[Seg], opts: &SimplifyOptions) -> Vec<Seg> {
         }
         let mut pts = Vec::new();
         for (k, s) in piece.iter().enumerate() {
-            let len = s.c.arclen(1e-6);
+            // Guarded: kurbo subdivides without end on huge finite coordinates.
+            let len = measured_arclen(&PathSeg::Cubic(s.c), 1e-6);
             let m = ((len / (tol * 0.5)).ceil() as usize).clamp(4, 256);
             sample(&s.c, m, &mut pts, k == 0);
         }
@@ -454,7 +456,7 @@ fn seam_error(original: &SubPath, before: &SubPath, fit: &SubPath, tol: f64) ->
         let mut pts = Vec::new();
         for j in (0..sp.segment_count()).filter(|&j| !seam_only || is_seam(j)) {
             let c = sp.segment(j);
-            let m = ((c.arclen(1e-6) / (tol.max(1e-6) * 0.5)).ceil() as usize).clamp(4, 256);
+            let m = ((measured_arclen(&PathSeg::Cubic(c), 1e-6) / (tol.max(1e-6) * 0.5)).ceil() as usize).clamp(4, 256);
             sample(&c, m, &mut pts, true);
         }
         pts