diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index b09c2af9..6c150300 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -331,6 +331,38 @@ fn revolve_and_primitives() {
     assert!(rel(m["total"]["volume_mm3"].as_f64().unwrap(), PI * 125.0 * 5.0 / 2.0) < 5e-4);
 }
 
+/// A spherical shell (a half ring between two arcs, both radial lines on the axis) revolved on a
+/// sketch plane that does not pass through the origin: the body is the shell, as it is on XY.
+/// Before, built in place, it measured a third too large (truck tessellates the degenerate faces
+/// on the axis reliably only with the axis through the origin).
+#[test]
+fn revolve_a_spherical_shell_off_the_origin() {
+    for (plane, z) in [(json!("XY"), 0.0), (json!({"origin": [0, 0, 10], "x_dir": [1, 0, 0], "y_dir": [0, 1, 0]}), 10.0)] {
+        let mut s = Session::default();
+        run(&mut s, "sketch.create", json!({"plane": plane, "name": "Ring"}));
+        run(&mut s, "sketch.line", json!({"points": [[-40, 0], [40, 0]]}));
+        run(&mut s, "sketch.arc.center_point", json!({"center": [0, 0], "start": [40, 0], "end": [-40, 0]}));
+        run(&mut s, "sketch.arc.center_point", json!({"center": [0, 0], "start": [18.5, 0], "end": [-18.5, 0]}));
+        run(&mut s, "sketch.finish", json!({}));
+        // The half ring: the larger of the two regions above the axis.
+        let si = run(&mut s, "sketch.inspect", json!({"sketch": "Ring"}));
+        let ring = si["profiles"]
+            .as_array()
+            .unwrap()
+            .iter()
+            .max_by(|a, b| a["area_mm2"].as_f64().unwrap().total_cmp(&b["area_mm2"].as_f64().unwrap()))
+            .unwrap()["index"]
+            .clone();
+        run(&mut s, "solid.revolve", json!({"sketch": "Ring", "profiles": [ring], "axis": "l1", "body_name": "Shell"}));
+        let m = run(&mut s, "inspect.measure", json!({"bodies": ["Shell"]}));
+        let want = 4.0 / 3.0 * PI * (40.0f64.powi(3) - 18.5f64.powi(3));
+        let v = m["total"]["volume_mm3"].as_f64().unwrap();
+        assert!(rel(v, want) < 5e-4, "plane at z {z}: {v} vs {want}");
+        let b = &m["bodies"][0]["bbox"];
+        assert!((b["min"][2].as_f64().unwrap() - (z - 40.0)).abs() < 1e-6 && (b["max"][2].as_f64().unwrap() - (z + 40.0)).abs() < 1e-6, "{b}");
+    }
+}
+
 #[test]
 fn sketch_tools_and_constraints() {
     let mut s = Session::default();
diff --git a/crates/kernel/src/build.rs b/crates/kernel/src/build.rs
index ade9ef80..8d0ca544 100644
--- a/crates/kernel/src/build.rs
+++ b/crates/kernel/src/build.rs
@@ -384,9 +384,25 @@ pub fn revolve(plane: &Plane, regions: &[Region2], axis_origin: Vec2, axis_dir:
             out.push(b);
             continue;
         }
-        let solid: Solid = guard("revolve", || Ok(builder::rsweep(&f, p3(o), v3(axis), mt::Rad(angle))))?;
+        // Edges on the axis (a spherical shell's two radial lines, say) sweep into degenerate faces
+        // there, which truck only tessellates reliably with the axis through the world origin. Off
+        // it, the body measured too large and booleans with it failed or removed the wrong side.
+        // Build such a profile there and move it into place, as `revolve_touching_axis` does.
+        let on_axis = |p: Vec2| d.cross(p - axis_origin).abs() < 1e-9;
+        let axis_edges = r.outer.segs.iter().filter(|s| matches!(**s, Seg2::Line { a, b } if on_axis(a) && on_axis(b))).count();
+        let shift = if axis_edges > 0 { o } else { Vec3::ZERO };
+        let (profile, f) = if shift.len() > 0.0 {
+            let local = Plane { origin: plane.origin - shift, ..*plane };
+            let profile = region_wires(&local, &given.oriented())?;
+            let f = attach_profile(&wires_of(&profile))?;
+            (profile, f)
+        } else {
+            (profile, f)
+        };
+        let solid: Solid = guard("revolve", || Ok(builder::rsweep(&f, p3(o - shift), v3(axis), mt::Rad(angle))))?;
         let closed = angle.abs() >= std::f64::consts::TAU;
         let history = guard("revolve history", || Ok(record::swept_face(&solid, &f, &seeds(&profile), closed)))?;
+        let solid = if shift.len() > 0.0 { builder::translated(&solid, v3(shift)) } else { solid };
         out.push(record::attach(Body::new(solid)?, &[], history, Default::default())?);
     }
     Ok(out)