diff --git a/src/entities/lwpolyline.rs b/src/entities/lwpolyline.rs
index 714ef2356..c9cc0d386 100644
--- a/src/entities/lwpolyline.rs
+++ b/src/entities/lwpolyline.rs
@@ -421,6 +421,9 @@ fn apply_transform(pline: &mut LwPolyline, t: &EntityTransform) {
     crate::scene::transform::apply_standard_entity_transform(pline, t, |entity, p1, p2| {
         for v in &mut entity.vertices {
             crate::scene::transform::reflect_xy_point(&mut v.location.x, &mut v.location.y, p1, p2);
+            // Bulge encodes which side the arc bows to; a reflection
+            // reverses it or every curved segment flips to the wrong side.
+            v.bulge = -v.bulge;
         }
     });
 }
diff --git a/src/entities/polyline.rs b/src/entities/polyline.rs
index ea222386d..4115ca6f3 100644
--- a/src/entities/polyline.rs
+++ b/src/entities/polyline.rs
@@ -475,6 +475,9 @@ impl Transformable for Polyline2D {
                     p1,
                     p2,
                 );
+                // Bulge encodes which side the arc bows to; a reflection
+                // reverses it or every curved segment flips to the wrong side.
+                v.bulge = -v.bulge;
             }
         });
     }