diff --git a/crates/engine/src/cmd/create.rs b/crates/engine/src/cmd/create.rs
index 84fa419a..3a9f6d67 100644
--- a/crates/engine/src/cmd/create.rs
+++ b/crates/engine/src/cmd/create.rs
@@ -167,15 +167,23 @@ pub fn parse_path_data(d: &str) -> Option<figcraft_geom::BezPath> {
 }
 
 /// How much a vector's path is scaled to take the size asked for: with both sides, each scales
-/// independently (as resizing a vector does); with one, the other keeps its proportion. A size
-/// asked for on an axis the geometry has none of is an error, not silently ignored.
+/// independently (as resizing a vector does); with one, the other keeps its proportion. A size on
+/// an axis the geometry has none of is an error unless it is 0 (a line's height), and a size of 0
+/// or less on an axis it has is refused rather than flattening it.
 fn vector_scale(width: Option<f64>, height: Option<f64>, bw: f64, bh: f64, what: &str) -> std::result::Result<(f64, f64), String> {
     let fit = |asked: Option<f64>, have: f64, axis: &str| match asked {
-        Some(a) if have > 1e-9 => Ok(a.max(0.0) / have),
-        Some(_) => Err(format!("`{axis}` can't size {what} with no {} extent", if axis == "width" { "horizontal" } else { "vertical" })),
         None => Ok(1.0),
+        Some(a) if have <= 1e-9 => {
+            if a == 0.0 {
+                Ok(1.0)
+            } else {
+                Err(format!("`{axis}` can't size {what} with no {} extent", if axis == "width" { "horizontal" } else { "vertical" }))
+            }
+        }
+        Some(a) if a > 0.0 && (a / have).is_finite() => Ok(a / have),
+        Some(_) => Err(format!("`{axis}` must be a positive, finite size: 0 or less would flatten {what}")),
     };
-    let (sx, sy) = match (width, height) {
+    Ok(match (width, height) {
         (Some(_), Some(_)) => (fit(width, bw, "width")?, fit(height, bh, "height")?),
         (Some(_), None) => {
             let s = fit(width, bw, "width")?;
@@ -186,11 +194,7 @@ fn vector_scale(width: Option<f64>, height: Option<f64>, bw: f64, bh: f64, what:
             (s, s)
         }
         (None, None) => (1.0, 1.0),
-    };
-    if sx <= 0.0 && sy <= 0.0 {
-        return Err(format!("`width` and `height` would make {what} 0×0"));
-    }
-    Ok((sx, sy))
+    })
 }
 
 pub fn create(s: &mut Session, p: &Value) -> Result<Value> {
diff --git a/crates/engine/src/vector_behaviour_tests.rs b/crates/engine/src/vector_behaviour_tests.rs
index 35d61074..fb734085 100644
--- a/crates/engine/src/vector_behaviour_tests.rs
+++ b/crates/engine/src/vector_behaviour_tests.rs
@@ -468,7 +468,32 @@ fn vector_paths_take_the_requested_size_and_refuse_empty_geometry() {
     assert!(e.contains("horizontal extent"), "{e}");
     let e = s.execute("vector.create", &json!({"path": "M0 0 L24 0", "height": 16})).unwrap_err().to_string();
     assert!(e.contains("vertical extent"), "{e}");
-    // A size that would collapse both axes is refused too.
-    let e = s.execute("vector.create", &json!({"path": path, "width": 0})).unwrap_err().to_string();
-    assert!(e.contains("0×0"), "{e}");
+    // But 0 on an axis it has none of is what it already is: a horizontal line with height 0.
+    let line = id_of(&ex(&mut s, "vector.create", json!({"path": "M0 0 L24 0", "width": 16, "height": 0}))["id"]).unwrap();
+    let n = s.doc().unwrap().node(line).unwrap();
+    assert_eq!((n.width, n.height), (16.0, 0.0));
+    // A size of 0 or less on an axis it has would flatten it, so it is refused, alone or with the other.
+    for p in [json!({"path": path, "width": 0}), json!({"path": path, "width": 16, "height": 0}), json!({"path": path, "width": -4, "height": 8})] {
+        let e = s.execute("vector.create", &p).unwrap_err().to_string();
+        assert!(e.contains("positive"), "{p}: {e}");
+    }
+}
+
+#[test]
+fn vector_points_take_the_requested_size() {
+    let mut s = Session::new();
+    let points = json!([[10, 20], [34, 20], [34, 32]]);
+    let corners = |s: &Session, id: NodeId| net(s, id).vertices.iter().map(|v| (v.x, v.y)).collect::<Vec<_>>();
+    // Both sides: each axis scales on its own; the vertices move with the box.
+    let both = id_of(&ex(&mut s, "vector.create", json!({"points": points, "x": 10, "y": 20, "width": 48, "height": 6}))["id"]).unwrap();
+    let n = s.doc().unwrap().node(both).unwrap();
+    assert_eq!((n.width, n.height), (48.0, 6.0));
+    assert_eq!(corners(&s, both), vec![(0.0, 0.0), (48.0, 0.0), (48.0, 6.0)]);
+    // One side: the other keeps its proportion.
+    let one = id_of(&ex(&mut s, "vector.create", json!({"points": points, "height": 24}))["id"]).unwrap();
+    let n = s.doc().unwrap().node(one).unwrap();
+    assert_eq!((n.width, n.height), (48.0, 24.0));
+    assert_eq!(corners(&s, one), vec![(0.0, 0.0), (48.0, 0.0), (48.0, 24.0)]);
+    let e = s.execute("vector.create", &json!({"points": points, "width": 16, "height": -1})).unwrap_err().to_string();
+    assert!(e.contains("positive"), "{e}");
 }