diff --git a/.changeset/green-jeans-rhyme.md b/.changeset/green-jeans-rhyme.md
new file mode 100644
index 000000000..cf0591d04
--- /dev/null
+++ b/.changeset/green-jeans-rhyme.md
@@ -0,0 +1,5 @@
+---
+"@hono/zod-validator": patch
+---
+
+Fix Hono RPC type inference when using zValidator with partial schemas.
diff --git a/packages/zod-validator/src/index.ts b/packages/zod-validator/src/index.ts
index 28e0030f2..791391b78 100644
--- a/packages/zod-validator/src/index.ts
+++ b/packages/zod-validator/src/index.ts
@@ -52,13 +52,9 @@ type ExtractValidationResponse<VF> = VF extends (value: any, c: any) => infer R
   : never
 
 type DefaultInput<Target extends keyof ValidationTargets, In, Out> = {
-  in: HasUndefined<In> extends true
-    ? {
-        [K in Target]?: [In] extends [ValidationTargets[K]] ? In : InferInput<In, K>
-      }
-    : {
-        [K in Target]: [In] extends [ValidationTargets[K]] ? In : InferInput<In, K>
-      }
+  in: {
+    [K in Target]: [In] extends [ValidationTargets[K]] ? In : InferInput<In, K>
+  }
   out: { [K in Target]: Out }
 }