diff --git a/src/app/features/galaxy-system/system-orbits-renderer.spec.ts b/src/app/features/galaxy-system/system-orbits-renderer.spec.ts
index 5ed9372..f498fd1 100644
--- a/src/app/features/galaxy-system/system-orbits-renderer.spec.ts
+++ b/src/app/features/galaxy-system/system-orbits-renderer.spec.ts
@@ -678,7 +678,9 @@ describe('solar-system bodies against Horizons', () => {
     return (spin.angleTo(new THREE.Vector3(0, 0, 1).applyQuaternion(line.quaternion)) * 180) / Math.PI;
   }
 
-  it('turns Venus, Uranus and Pluto backwards against their orbits, at the tilts Horizons gives', () => {
+  it('turns Venus, Uranus and Pluto backwards against their orbits, at the tilts Horizons gives the first two', () => {
+    // Pluto's Horizons page gives no tilt; 119.6 is the one its IAU pole makes with its orbit, so for
+    // Pluto this checks that its pole and W are drawn as the kernel gives them, not the pole itself.
     // The IAU names a planet's north pole by the side of the solar system it lies on, so Venus's W
     // and Uranus's run backwards; Pluto's pole follows the right-hand rule instead, and points
     // south. Either way the spin read off the drawn sphere is past 90 degrees from the orbit's pole.
diff --git a/tools/etl/build.ts b/tools/etl/build.ts
index d4dfd08..a8abb94 100644
--- a/tools/etl/build.ts
+++ b/tools/etl/build.ts
@@ -209,6 +209,10 @@ const DAY_OFFSET_CEILINGS: Record<string, number> = { neptune: 0.01 };
  * a planet's north pole by the side of the solar system it lies on, whichever way the planet turns.
  * Measured on this catalogue: at most 0.058 degrees (Venus, 177.358 against 177.3). Taken as the
  * pole alone, Venus comes out at 2.6 degrees and Uranus at 82.2, which is what this catches.
+ *
+ * Pluto's Horizons page states no obliquity: its 119.6 is worked out from the IAU pole itself (see
+ * `BodySpec.obliquityDeg`), so for Pluto this checks only that the kernel's pole and W were read as
+ * written, not the pole against a second source.
  */
 const MAX_OBLIQUITY_OFFSET_DEG = 0.1;
 
@@ -327,7 +331,7 @@ function validateBodies(bodies: BodyRecord[], horizonsOrbits: Map<string, Orbita
         const obliquity = angleBetweenDeg(axis, body.laplacePole ? laplacePlaneToEquatorial(normal, body.laplacePole) : eclipticToEquatorial(normal));
         assertCondition(
           Math.abs(obliquity - body.obliquityDeg) <= MAX_OBLIQUITY_OFFSET_DEG,
-          `${body.name}'s IAU spin axis is ${obliquity.toFixed(3)} degrees from its orbit's pole, where Horizons gives an obliquity of ${body.obliquityDeg} (at most ${MAX_OBLIQUITY_OFFSET_DEG} apart expected) — the pole or the sense of W was read wrongly.`
+          `${body.name}'s IAU spin axis is ${obliquity.toFixed(3)} degrees from its orbit's pole, where ${body.id === 'pluto' ? 'its IAU pole' : 'Horizons'} gives an obliquity of ${body.obliquityDeg} (at most ${MAX_OBLIQUITY_OFFSET_DEG} apart expected) — the pole or the sense of W was read wrongly.`
         );
         spins.push(`${body.id} tilt ${obliquity.toFixed(3)}`);
       }