diff --git a/crates/ui-egui/src/grid.rs b/crates/ui-egui/src/grid.rs
index 5b956cf8e..7f16c83da 100644
--- a/crates/ui-egui/src/grid.rs
+++ b/crates/ui-egui/src/grid.rs
@@ -1230,7 +1230,10 @@ pub(crate) fn paint_quadrant(
             p.with_clip_rect(rect.intersect(p.clip_rect())).galley(pos2(x, y), galley, color);
             continue;
         }
-        let first_line = text.lines().next().unwrap_or("").to_string();
+        // Wrap Text off: Excel ignores the line breaks and draws the whole string on one line.
+        let first_line: String = text.chars().filter(|&ch| ch != '\n' && ch != '\r').collect();
+        // The fill position indexes `text`; move it back by the breaks removed before it.
+        let fill_char = fill_char.map(|(ch, pos)| (ch, pos.saturating_sub(text.get(..pos).map_or(0, |s| s.matches(['\n', '\r']).count()))));
         // Shrink to fit: too-wide content is drawn in a smaller font so it fits the cell (or the
         // merged area): it neither spills, nor is clipped, nor turns into ####.
         let small = (st.align.shrink && !rotated && st.align.h != HAlign::Fill && fill_char.is_none())
diff --git a/crates/ui-egui/tests/nowrap_line_breaks.rs b/crates/ui-egui/tests/nowrap_line_breaks.rs
new file mode 100644
index 000000000..413f441d0
--- /dev/null
+++ b/crates/ui-egui/tests/nowrap_line_breaks.rs
@@ -0,0 +1,40 @@
+//! Line breaks with Wrap Text off (#1604): Excel ignores them and draws the whole string on one line.
+
+use egui::Shape;
+use gridcraft_engine::Session;
+use serde_json::json;
+
+type Harness = egui_kittest::Harness<'static, gridcraft_ui_egui::SheetApp>;
+
+fn harness() -> Harness {
+    let mut s = Session::new();
+    s.new_workbook();
+    s.execute("cell.set", json!({"cell": "A1", "input": "Active\n\nUnits: LF 2x10\r\nBand: 60-20000 Hz"})).unwrap();
+    // Typing a break turns Wrap Text on; a file can still store the text with it off.
+    s.execute("home.formatCells", json!({"range": "A1", "style": {"align": {"wrap": false}}})).unwrap();
+    s.execute("cell.set", json!({"cell": "A3", "input": "Wrapped\nText"})).unwrap();
+    s.execute("home.formatCells", json!({"range": "A3", "style": {"align": {"wrap": true}}})).unwrap();
+    s.execute("selection.set", json!({"range": "H20"})).unwrap();
+    let mut h = egui_kittest::Harness::builder().with_size(egui::vec2(1200.0, 800.0)).build_ui_state(
+        |ui, app: &mut gridcraft_ui_egui::SheetApp| {
+            app.logic(ui.ctx());
+            app.ui(ui);
+        },
+        gridcraft_ui_egui::SheetApp::new(s, Default::default()),
+    );
+    h.run_steps(4);
+    h
+}
+
+fn painted(h: &Harness, text: &str) -> bool {
+    h.output().shapes.iter().any(|s| matches!(&s.shape, Shape::Text(t) if t.galley.job.text == text))
+}
+
+#[test]
+fn unwrapped_cell_draws_every_line_on_one_line() {
+    let h = harness();
+    assert!(painted(&h, "ActiveUnits: LF 2x10Band: 60-20000 Hz"), "A1 draws the whole string without its breaks");
+    assert!(!painted(&h, "Active"), "A1 is not cut at its first break");
+    // Wrap Text on keeps the breaks.
+    assert!(painted(&h, "Wrapped\nText"));
+}