diff --git a/scripts/genesis/AccountCreator.ts b/scripts/genesis/AccountCreator.ts
index 96e416ff..e12c4aaf 100644
--- a/scripts/genesis/AccountCreator.ts
+++ b/scripts/genesis/AccountCreator.ts
@@ -233,6 +233,7 @@ export class LocalDevAccountCreator {
 }
 
 const ED25519_PUBLIC_KEY_HEX_LENGTH = 66 // 0x prefix + 64 hex chars (32 bytes)
+const VALIDATOR_ID_REGEX = /^[1-9][0-9]*$/
 
 function parseOverridePublicKeys(input: string): Map<number, Hex> {
   const map = new Map<number, Hex>()
@@ -252,9 +253,12 @@ function parseOverridePublicKeys(input: string): Map<number, Hex> {
       throw new Error(`Invalid format in overridePublicKeys: ${entry} (missing ID or key)`)
     }
 
-    const id = Number(idStr)
+    if (!VALIDATOR_ID_REGEX.test(idStr)) {
+      throw new Error(`Invalid validator ID in overridePublicKeys: ${idStr}`)
+    }
 
-    if (isNaN(id) || id < 1) {
+    const id = Number(idStr)
+    if (!Number.isSafeInteger(id)) {
       throw new Error(`Invalid validator ID in overridePublicKeys: ${idStr}`)
     }
     if (map.has(id)) {
diff --git a/tests/unit/localdev-account-creator.test.ts b/tests/unit/localdev-account-creator.test.ts
new file mode 100644
index 00000000..7d753e8f
--- /dev/null
+++ b/tests/unit/localdev-account-creator.test.ts
@@ -0,0 +1,40 @@
+// Copyright 2026 Circle Internet Group, Inc. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import { expect } from 'chai'
+import { LocalDevAccountCreator } from '../../scripts/genesis/AccountCreator'
+
+const publicKey = `0x${'11'.repeat(32)}`
+
+describe('LocalDevAccountCreator', () => {
+  describe('overridePublicKeys', () => {
+    it('accepts canonical decimal validator IDs', () => {
+      const creator = new LocalDevAccountCreator({ overridePublicKeys: `1:${publicKey},42:${publicKey}` })
+
+      expect(creator.overridePublicKeys.get(1)).to.equal(publicKey)
+      expect(creator.overridePublicKeys.get(42)).to.equal(publicKey)
+    })
+
+    it('rejects non-canonical validator IDs', () => {
+      for (const id of ['1.5', '1e0', '01', '-1', 'NaN', 'Infinity', '']) {
+        expect(
+          () => new LocalDevAccountCreator({ overridePublicKeys: `${id}:${publicKey}` }),
+          `${id} should be rejected`,
+        ).to.throw(/Invalid validator ID|missing ID/)
+      }
+    })
+  })
+})