diff --git a/crates/engine/src/cmd/develop.rs b/crates/engine/src/cmd/develop.rs
index 6a68ee337..37406fab4 100644
--- a/crates/engine/src/cmd/develop.rs
+++ b/crates/engine/src/cmd/develop.rs
@@ -678,10 +678,11 @@ pub fn specs() -> Vec<CommandSpec> {
             let (w, h) = crop_dims(s, id);
             edit(s, "crop.rotateAspect", "Rotate Crop", |d| {
                 let r = d.crop.geometry.rect_px(w, h);
-                let a = r.height() / r.width();
+                // a degenerate crop has no aspect to rotate: fall back to the image's own
+                let a = Some(r.height() / r.width()).filter(|a| a.is_finite() && *a > 0.0);
                 d.crop.aspect = d.crop.aspect.map(|(x, y)| (y, x));
                 let angle = d.crop.geometry.angle;
-                d.crop.geometry = crop_fit_angle(w, h, angle, Some(a));
+                d.crop.geometry = crop_fit_angle(w, h, angle, a);
                 Ok(())
             })
         }),
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index aeb7d4426..cad681f20 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -474,6 +474,21 @@ fn degenerate_crops_render_with_spots_and_masks() {
     }
 }
 
+/// `crop.rotateAspect` on a crop of no size took its aspect from 0/0 = NaN and stored a NaN crop
+/// rectangle; it now falls back to the image's own aspect, a finite crop inside the image.
+#[test]
+fn rotate_aspect_of_degenerate_crop_stays_finite() {
+    for rect in [[0.5, 0.5, 0.5, 0.5], [0.2, 0.2, 0.2, 0.8], [0.2, 0.2, 0.8, 0.2]] {
+        let mut s = demo();
+        s.execute("crop.set", &json!({"rect": rect})).unwrap();
+        s.execute("crop.rotateAspect", &json!({})).unwrap();
+        let r = active_dev(&s).crop.geometry.rect;
+        assert!([r.x0, r.y0, r.x1, r.y1].iter().all(|v| v.is_finite()), "{rect:?}: {r:?}");
+        assert!(r.width() > 0.0 && r.height() > 0.0, "{rect:?}: {r:?}");
+        assert!(r.x0 >= 0.0 && r.y0 >= 0.0 && r.x1 <= 1.0 && r.y1 <= 1.0, "{rect:?}: {r:?}");
+    }
+}
+
 /// `mask.move` with a delta near `i64::MAX` overflowed `index + delta` (a panic wherever overflow
 /// checks are on); extreme deltas and indices now move the mask to the bottom or the top.
 #[test]
diff --git a/crates/geom/src/lib.rs b/crates/geom/src/lib.rs
index 4b8f623e2..14eaaf065 100644
--- a/crates/geom/src/lib.rs
+++ b/crates/geom/src/lib.rs
@@ -178,7 +178,7 @@ impl Rect {
     }
     /// Largest rectangle of aspect `a` (w/h) centred in `self`.
     pub fn fit_aspect(&self, a: f64) -> Rect {
-        if a <= 0.0 || self.is_empty() {
+        if !(a.is_finite() && a > 0.0) || self.is_empty() {
             return *self;
         }
         let (w, h) = (self.width(), self.height());