diff --git a/frontend/src/lib/store.contract.test.ts b/frontend/src/lib/store.contract.test.ts
index 66aa18dc..04e397b4 100644
--- a/frontend/src/lib/store.contract.test.ts
+++ b/frontend/src/lib/store.contract.test.ts
@@ -15,7 +15,7 @@ describe("a store's use()", () => {
       for (const m of src.matchAll(/\b\w+\.use\(\)/g)) {
         const before = src.slice(0, m.index);
         const owners = [...before.matchAll(/(?:function\s+(\w+)|const\s+(\w+)\s*=\s*\()/g)];
-        const owner = owners.at(-1);
+        const owner = owners[owners.length - 1];
         const name = owner?.[1] ?? owner?.[2] ?? "";
         if (!name.startsWith("use")) offenders.push(`${f}: ${m[0]} in ${name || "?"}`);
       }