diff --git a/packages/zod/.gitignore b/packages/zod/.gitignore
index 225074551..86d865467 100644
--- a/packages/zod/.gitignore
+++ b/packages/zod/.gitignore
@@ -4,3 +4,4 @@
 **/*.d.ts
 **/*.d.mts
 **/*.d.cts
+**/package.json
diff --git a/packages/zod/src/v4/classic/tests/string.test.ts b/packages/zod/src/v4/classic/tests/string.test.ts
index 5e32b9256..a223b878c 100644
--- a/packages/zod/src/v4/classic/tests/string.test.ts
+++ b/packages/zod/src/v4/classic/tests/string.test.ts
@@ -920,6 +920,8 @@ test("CIDR v6 validation", () => {
   expect(cidrV6.safeParse("not a cidr").success).toBe(false); // Invalid format
   expect(cidrV6.safeParse("192.168.0.0/24").success).toBe(false); // IPv4 CIDR in v6 validation
   expect(cidrV6.safeParse("2001:0db8:85a3::/64/whatever-after").success).toBe(false);
+  expect(cidrV6.safeParse("22d9:f4a8:6a90:f3bf:dcaa:2beb:5fba:0000/112").success).toBe(true);
+  expect(cidrV6.safeParse("22d9:f4a8:6a90:f3bf:dcaa:2beb:5fba:0000/112/268").success).toBe(false);
 });
 
 test("E.164 validation", () => {
diff --git a/packages/zod/src/v4/core/schemas.ts b/packages/zod/src/v4/core/schemas.ts
index b410d79dd..98aa588b1 100644
--- a/packages/zod/src/v4/core/schemas.ts
+++ b/packages/zod/src/v4/core/schemas.ts
@@ -830,10 +830,11 @@ export const $ZodCIDRv6: core.$constructor<$ZodCIDRv6> = /*@__PURE__*/ core.$con
     $ZodStringFormat.init(inst, def);
 
     inst._zod.check = (payload) => {
-      const segments = payload.value.split("/");
-      const [address, prefix] = segments;
+      const parts = payload.value.split("/");
       try {
-        if (segments.length !== 2) throw new Error();
+        if (parts.length !== 2) throw new Error();
+        const [address, prefix] = parts;
+        if (!prefix) throw new Error();
         const prefixNum = Number(prefix);
         if (`${prefixNum}` !== prefix) throw new Error();
         if (prefixNum < 0 || prefixNum > 128) throw new Error();
@@ -1763,7 +1764,7 @@ export interface $ZodObject<
 function normalizeDef(def: $ZodObjectDef) {
   const keys = Object.keys(def.shape);
   for (const k of keys) {
-    if (!def.shape[k]._zod.traits.has("$ZodType")) {
+    if (!def.shape?.[k]?._zod?.traits?.has("$ZodType")) {
       throw new Error(`Invalid element at key "${k}": expected a Zod schema`);
     }
   }