diff --git a/frontend/src/certs/Registers/index.tsx b/frontend/src/certs/Registers/index.tsx
index e969184..f6ba470 100644
--- a/frontend/src/certs/Registers/index.tsx
+++ b/frontend/src/certs/Registers/index.tsx
@@ -1,4 +1,4 @@
-import { For, Match, Show, createEffect, createMemo, createSignal } from "solid-js";
+import { For, Show, createEffect, createMemo, createSignal } from "solid-js";
 import { Person } from "../../types/Person";
 import { Register } from "../../types/Register";
 import { courseMap } from "../../utils/allCourses";
@@ -159,12 +159,13 @@ function RegisterEl(props: {register: Register, person: Person, onClick: () => v
             ? ""
             : customLabelsMap()[register.register_custom_label]?.custom_label_value ?? "";
 
+        const certCode = register.register_is_preview ? "0000" : register.register_code.toString().padStart(4, "0");
 
         generator(`${courseN} - ${personFullName}.docx`, {
             matpel: null,
             personFullName,
             personDni: person.person_dni.toString(),
-            certCode: register.register_code.toString().padStart(4, "0"),
+            certCode,
             certYear: year,
             certMonth: month,
             certDay: day,