diff --git a/package-lock.json b/package-lock.json
index 0ad464e..da6ae2e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -28,7 +28,7 @@
       "peerDependencies": {
         "luxon": "^3.5.0",
         "typescript": "^5.7.3",
-        "zod": "3.25.76"
+        "zod": "4.0.14"
       }
     },
     "node_modules/@babel/helper-string-parser": {
@@ -5837,9 +5837,9 @@
       }
     },
     "node_modules/zod": {
-      "version": "3.25.76",
-      "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
-      "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
+      "version": "4.0.14",
+      "resolved": "https://registry.npmjs.org/zod/-/zod-4.0.14.tgz",
+      "integrity": "sha512-nGFJTnJN6cM2v9kXL+SOBq3AtjQby3Mv5ySGFof5UGRHrRioSJ5iG680cYNjE/yWk671nROcpPj4hAS8nyLhSw==",
       "license": "MIT",
       "peer": true,
       "funding": {
diff --git a/package.json b/package.json
index f440f21..6720946 100644
--- a/package.json
+++ b/package.json
@@ -60,7 +60,7 @@
   "peerDependencies": {
     "luxon": "^3.5.0",
     "typescript": "^5.7.3",
-    "zod": "3.25.76"
+    "zod": "4.0.14"
   },
   "dependencies": {
     "radashi": "^12.6.0"
diff --git a/src/schemas/pricing.ts b/src/schemas/pricing.ts
index 38753f8..a8ec4cf 100644
--- a/src/schemas/pricing.ts
+++ b/src/schemas/pricing.ts
@@ -20,12 +20,12 @@ export const tierMapSchema = z.object({
   better: tierDetailsRawSchema,
   best: tierDetailsRawSchema
 });
-export const tierIds = Object.keys(tierMapSchema.shape) as Array<keyof z.infer<typeof tierMapSchema>>;
+export const tierIds = Object.keys(tierMapSchema.shape) as ReadonlyArray<keyof z.infer<typeof tierMapSchema>>;
 
 export const topupMapSchema = z.object({
   single: productRawSchema
 });
-export const topupIds = Object.keys(topupMapSchema.shape) as Array<keyof z.infer<typeof topupMapSchema>>;
+export const topupIds = Object.keys(topupMapSchema.shape) as ReadonlyArray<keyof z.infer<typeof topupMapSchema>>;
 
 export const customerPortalFlowTypeSchema = z.enum([
   'subscription_cancel',
diff --git a/src/types/pricing.ts b/src/types/pricing.ts
index fa5f16c..a50d7e3 100644
--- a/src/types/pricing.ts
+++ b/src/types/pricing.ts
@@ -7,13 +7,13 @@ import type {
 } from '@schemas';
 import type z from 'zod';
 
-export type TierId = keyof z.input<typeof tierMapSchema>;
+export type TierId = keyof z.infer<typeof tierMapSchema>;
 export type Tier = z.infer<typeof tierDetailsRawSchema>;
 export type TierMap = {
   [K in TierId]: Tier;
 };
 
-export type TopupId = keyof z.input<typeof topupMapSchema>;
+export type TopupId = keyof z.infer<typeof topupMapSchema>;
 export type Topup = z.infer<typeof productRawSchema>;
 export type TopupMap = {
   [K in TopupId]: Topup;