diff --git a/crates/ui-egui/src/addons/cutting/tests.rs b/crates/ui-egui/src/addons/cutting/tests.rs
index 39adb0539f..2e69eab904 100644
--- a/crates/ui-egui/src/addons/cutting/tests.rs
+++ b/crates/ui-egui/src/addons/cutting/tests.rs
@@ -118,4 +118,28 @@ fn weed_box_and_lines_previews_cancels_and_runs_on_ok() {
     crate::dialogs::set_field(d, "spacing".into(), json!(20));
     crate::dialogs::confirm(&mut app).unwrap();
     assert_eq!(count(&app), nodes + 8, "a group, the box and six pieces of line");
+
+    // A Spacing below 0 is refused, not swapped for the Count.
+    app.run("edit.undo", json!({})).unwrap();
+    app.run("select.set", json!({"ids": [id]})).unwrap();
+    open(&mut app);
+    let n = steps(&app);
+    crate::dialogs::set_field(app.ui.dialog.as_mut().unwrap(), "spacing".into(), json!(-5));
+    let e = crate::dialogs::confirm(&mut app).unwrap_err().to_string();
+    assert!(e.contains("`spacing` must be more than 0"), "{e}");
+    assert_eq!(steps(&app), n, "no undo step");
+
+    // A Spacing with no value, or of 0 written with its unit, leaves the Count in use: a Count of 0
+    // draws the box alone.
+    crate::dialogs::cancel(&mut app);
+    for spacing in [serde_json::Value::Null, json!("0 pt")] {
+        app.run("select.set", json!({"ids": [id]})).unwrap();
+        open(&mut app);
+        let d = app.ui.dialog.as_mut().unwrap();
+        crate::dialogs::set_field(d, "spacing".into(), spacing.clone());
+        crate::dialogs::set_field(d, "count".into(), json!(0));
+        crate::dialogs::confirm(&mut app).unwrap();
+        assert_eq!(count(&app), nodes + 2, "{spacing}: a group and the box");
+        app.run("edit.undo", json!({})).unwrap();
+    }
 }
diff --git a/crates/ui-egui/src/dialogs/command.rs b/crates/ui-egui/src/dialogs/command.rs
index 374868e27f..2e277caea8 100644
--- a/crates/ui-egui/src/dialogs/command.rs
+++ b/crates/ui-egui/src/dialogs/command.rs
@@ -87,13 +87,18 @@ fn call(d: &Dialog) -> (String, Value) {
     {
         o.remove("rowGutter");
     }
-    // Weed Box and Lines: a Spacing above 0 divides the box instead of the Count, and only the one
-    // in use is sent.
+    // Weed Box and Lines: a Spacing of 0, or none, leaves the Count in use; any other Spacing is
+    // sent instead of the Count, so the command refuses one below 0.
     if d.str("__command") == crate::addons::cutting::WEED
         && let Some(o) = params.as_object_mut()
     {
-        let by_spacing = o.get("spacing").and_then(Value::as_f64).is_some_and(|s| s > 0.0);
-        o.remove(if by_spacing { "count" } else { "spacing" });
+        let zero = |s: &Value| match s {
+            Value::Null => true,
+            Value::String(t) => vectorcraft_doc::Unit::Points.parse(t).or_else(|| t.trim().parse().ok()) == Some(0.0),
+            v => v.as_f64() == Some(0.0),
+        };
+        let by_count = o.get("spacing").is_none_or(zero);
+        o.remove(if by_count { "spacing" } else { "count" });
     }
     (d.str("__command"), params)
 }