diff --git a/crates/ui-egui/src/dialogs/form.rs b/crates/ui-egui/src/dialogs/form.rs
index b1e9a9b75..2b3ace0d0 100644
--- a/crates/ui-egui/src/dialogs/form.rs
+++ b/crates/ui-egui/src/dialogs/form.rs
@@ -248,7 +248,7 @@ pub(super) fn param_fields(
             match v {
                 Value::Number(n) => {
                     if let Some(x) = crate::widgets::plain_field(ui, ("fx-num", &k), n.as_f64().unwrap_or(0.0), "", 3, 140.0) {
-                        d.fields.insert(k, json!(x));
+                        d.fields.insert(k, typed_number(x));
                         changed = true;
                     }
                 }
@@ -291,6 +291,13 @@ pub(super) fn param_fields(
     changed
 }
 
+/// A number typed in a command's dialog as JSON: a whole number as an integer, as counts are read
+/// (`as_u64`: Object Mosaic's columns and rows, #1000), which `12.0` isn't; a fraction stays one.
+/// Commands that take any number read either.
+fn typed_number(x: f64) -> Value {
+    if x.fract() == 0.0 && x.abs() < 1e15 { json!(x as i64) } else { json!(x) }
+}
+
 /// Editor for a plug-in's parameters from its schema (plug-in filter and effect dialogs): numbers
 /// within their range, whole numbers, checkboxes and dropdowns, in declaration order. Returns
 /// true when a value changed. The labels (from the parameter keys) and choices are the plug-in's
@@ -552,3 +559,19 @@ pub(super) fn caption(ui: &mut egui::Ui, text: &str) {
     let t = Tokens::get(ui.ctx());
     ui.label(egui::RichText::new(tl!(text)).size(11.0).color(t.text_dim));
 }
+
+#[cfg(test)]
+mod typed_number_tests {
+    use super::*;
+
+    #[test]
+    fn whole_numbers_are_integers_and_fractions_stay_fractions() {
+        // Whatever the field held before: a count typed after a fraction is a count again.
+        assert_eq!(typed_number(24.0).as_u64(), Some(24));
+        assert_eq!(typed_number(-4.0), json!(-4));
+        assert_eq!(typed_number(0.0), json!(0));
+        assert_eq!(typed_number(2.5), json!(2.5));
+        // Numbers past exact integers stay floats.
+        assert!(typed_number(1e20).is_f64());
+    }
+}
diff --git a/crates/ui-egui/src/dialogs/tests.rs b/crates/ui-egui/src/dialogs/tests.rs
index f9534577b..f0df5c695 100644
--- a/crates/ui-egui/src/dialogs/tests.rs
+++ b/crates/ui-egui/src/dialogs/tests.rs
@@ -434,6 +434,38 @@ fn a_dialog_opens_with_its_first_field_focused_so_typing_and_enter_apply() {
     assert_eq!(node.appearance.effects.last().map(|e| e.params["scaleH"].clone()), Some(json!(50.0)));
 }
 
+/// #1000: a count typed in Object › Create Object Mosaic… reaches the command (a whole number typed
+/// in a command's dialog is an integer), so the mosaic has that many columns, not the 10 × 10 grid.
+#[test]
+fn object_mosaic_makes_the_grid_typed_in_its_dialog() {
+    let mut app = app();
+    app.run("shape.rectangle", json!({"x": 10, "y": 10, "width": 60, "height": 40})).unwrap();
+    app.run("object.rasterize", json!({"ppi": 72})).unwrap();
+    let ctx = egui::Context::default();
+    theme::install_fonts(&ctx);
+    theme::apply(&ctx, Default::default());
+    let frame = |app: &mut VectorcraftApp, events: Vec<egui::Event>| {
+        let mut out = ctx.run_ui(egui::RawInput { events, ..Default::default() }, |ui| show(app, ui.ctx()));
+        out.textures_delta.clear();
+    };
+    let entry = crate::menus::menu_entries(&app).into_iter().find(|e| e.label == "Create Object Mosaic…").expect("menu item");
+    let (cmd, params) = crate::menus::click_target(&entry.label, entry.command.as_deref().unwrap(), &entry.params);
+    crate::menus::invoke(&mut app, &cmd, params);
+    // Its first field, Columns, is focused: type 3 over it and press Enter.
+    frame(&mut app, vec![]);
+    frame(&mut app, vec![egui::Event::Text("3".into())]);
+    let enter = egui::Event::Key { key: egui::Key::Enter, physical_key: None, pressed: true, repeat: false, modifiers: Default::default() };
+    frame(&mut app, vec![enter]);
+    assert!(app.ui.dialog.is_none());
+    let mut tiles = None;
+    app.session.doc().unwrap().doc.walk(|n| {
+        if n.name.as_deref() == Some("Object Mosaic") {
+            tiles = n.children().map(|c| c.len());
+        }
+    });
+    assert_eq!(tiles, Some(3 * 10));
+}
+
 /// #793: Artboard Options lists its fields as Name, Width, Height, not by key.
 #[test]
 fn artboard_options_lists_name_then_width_and_height() {