diff --git a/crates/engine/src/cmd/hatch.rs b/crates/engine/src/cmd/hatch.rs
index 5a77e9346..5e2a0fa7a 100644
--- a/crates/engine/src/cmd/hatch.rs
+++ b/crates/engine/src/cmd/hatch.rs
@@ -113,7 +113,8 @@ fn closed_loop(d: &Drawing, e: &Entity) -> Option<Vec<PolyVertex>> {
 }
 
 /// Open curves that can make up an island together (a square drawn as four LINEs, two ARCs
-/// forming a circle). Closed objects are islands on their own (see `closed_loop`).
+/// forming a circle, the inner lines of multiline walls around a room). Closed objects are
+/// islands on their own (see `closed_loop`).
 fn island_curve(d: &Drawing, e: &Entity) -> bool {
     matches!(
         e.kind,
@@ -123,6 +124,7 @@ fn island_curve(d: &Drawing, e: &Entity) -> bool {
             | EntityKind::LwPolyline(_)
             | EntityKind::Polyline3d(_)
             | EntityKind::Spline(_)
+            | EntityKind::MLine(_)
     ) && closed_loop(d, e).is_none()
 }
 
diff --git a/crates/engine/tests/it/hatch_options.rs b/crates/engine/tests/it/hatch_options.rs
index d309df165..a26d1bd58 100644
--- a/crates/engine/tests/it/hatch_options.rs
+++ b/crates/engine/tests/it/hatch_options.rs
@@ -249,3 +249,13 @@ fn hatchedit_refuses_unknown_patterns_and_region_boundaries() {
     // Region boundaries need REGION objects; the hatch is left as it was.
     assert!(s.execute("hatchedit", &json!({ "handles": [h], "recreate": "region" })).is_err());
 }
+
+#[test]
+fn multiline_wall_hatch_keeps_the_room_as_an_island() {
+    // A closed multiline wall: picking inside the wall hatches the band between its outer and
+    // inner lines; the room the inner lines enclose is an island, not filled.
+    let mut s = Session::new();
+    s.execute("mline", &json!({ "points": [[0, 0], [10, 0], [10, 10], [0, 10]], "closed": true, "scale": 1, "justification": "zero" })).unwrap();
+    let h = handle(&s.execute("hatch", &json!({ "points": [[0, 5]], "pattern": "SOLID" })).unwrap());
+    assert_eq!(hatch(&s, &h).loops.len(), 2, "outer face + the room as an island");
+}