diff --git a/frontend/src/widgets/ReservedControls.test.tsx b/frontend/src/widgets/ReservedControls.test.tsx
index e607e7ec..98e35b19 100644
--- a/frontend/src/widgets/ReservedControls.test.tsx
+++ b/frontend/src/widgets/ReservedControls.test.tsx
@@ -21,3 +21,17 @@ test("other reveals a textarea and emits freetext with the typed text", async ()
   await userEvent.click(screen.getByRole("button", { name: /send/i }));
   expect(onControl).toHaveBeenCalledWith("freetext", "usa la tabella X");
 });
+
+test("Send stays disabled until non-whitespace text is entered", async () => {
+  const onControl = vi.fn();
+  render(<ReservedControls reserved={["other"]} onControl={onControl} />);
+  await userEvent.click(screen.getByRole("button", { name: /other — specify/i }));
+  const send = screen.getByRole("button", { name: /send/i });
+  expect(send).toBeDisabled();
+  await userEvent.type(screen.getByRole("textbox"), "   ");
+  expect(send).toBeDisabled();
+  await userEvent.click(send);
+  expect(onControl).not.toHaveBeenCalled();
+  await userEvent.type(screen.getByRole("textbox"), "ok");
+  expect(send).not.toBeDisabled();
+});
diff --git a/frontend/src/widgets/ReservedControls.tsx b/frontend/src/widgets/ReservedControls.tsx
index 7fd37e7f..821c1a31 100644
--- a/frontend/src/widgets/ReservedControls.tsx
+++ b/frontend/src/widgets/ReservedControls.tsx
@@ -32,7 +32,11 @@ export function ReservedControls({
             value={text}
             onChange={(e) => setText(e.target.value)}
           />
-          <button className="text-sm border rounded px-2 py-1 self-start" onClick={() => onControl("freetext", text)}>
+          <button
+            className="text-sm border rounded px-2 py-1 self-start disabled:opacity-50 disabled:cursor-not-allowed"
+            disabled={!text.trim()}
+            onClick={() => onControl("freetext", text)}
+          >
             Send
           </button>
         </div>