diff --git a/coercion.ts b/coercion.ts
index 85f1ad7..e634ab0 100644
--- a/coercion.ts
+++ b/coercion.ts
@@ -218,63 +218,83 @@ export function enableTypeCoercion<
       wrap: optional,
       default: type.getDefault,
     });
-    schema = options?.wrap
-      ? "default" in options
-        ? options.wrap(schema, options.default)
-        : options.wrap(schema)
-      : schema;
+    schema = coerce(
+      options?.wrap
+        ? "default" in options
+          ? options.wrap(schema, options.default)
+          : options.wrap(schema)
+        : schema,
+      (output) => coerceString(output),
+    );
   } else if (type.type === "nullish") {
     schema = enableTypeCoercion(type.wrapped, {
       wrap: nullish,
       default: type.getDefault,
     });
-    schema = options?.wrap
-      ? "default" in options
-        ? options.wrap(schema, options.default)
-        : options.wrap(schema)
-      : schema;
+    schema = coerce(
+      options?.wrap
+        ? "default" in options
+          ? options.wrap(schema, options.default)
+          : options.wrap(schema)
+        : schema,
+      (output) => coerceString(output),
+    );
   } else if (type.type === "nullable") {
     schema = enableTypeCoercion(type.wrapped, {
       wrap: nullable,
       default: type.getDefault,
     });
-    schema = options?.wrap
-      ? "default" in options
-        ? options.wrap(schema, options.default)
-        : options.wrap(schema)
-      : schema;
+    schema = coerce(
+      options?.wrap
+        ? "default" in options
+          ? options.wrap(schema, options.default)
+          : options.wrap(schema)
+        : schema,
+      (output) => coerceString(output),
+    );
   } else if (type.type === "non_optional") {
     schema = enableTypeCoercion(type.wrapped, { wrap: nonOptional });
-    schema = options?.wrap
-      ? "default" in options
-        ? options.wrap(schema, options.default)
-        : options.wrap(schema)
-      : schema;
+    schema = coerce(
+      options?.wrap
+        ? "default" in options
+          ? options.wrap(schema, options.default)
+          : options.wrap(schema)
+        : schema,
+      (output) => coerceString(output),
+    );
   } else if (type.type === "non_nullish") {
     schema = enableTypeCoercion(type.wrapped, { wrap: nonNullish });
-    schema = options?.wrap
-      ? "default" in options
-        ? options.wrap(schema, options.default)
-        : options.wrap(schema)
-      : schema;
+    schema = coerce(
+      options?.wrap
+        ? "default" in options
+          ? options.wrap(schema, options.default)
+          : options.wrap(schema)
+        : schema,
+      (output) => coerceString(output),
+    );
   } else if (type.type === "non_nullable") {
     schema = enableTypeCoercion(type.wrapped, { wrap: nonNullable });
-    schema = options?.wrap
-      ? "default" in options
-        ? options.wrap(schema, options.default)
-        : options.wrap(schema)
-      : schema;
+    schema = coerce(
+      options?.wrap
+        ? "default" in options
+          ? options.wrap(schema, options.default)
+          : options.wrap(schema)
+        : schema,
+      (output) => coerceString(output),
+    );
   } else if (type.type === "union") {
     // @ts-expect-error
     schema = union(type.options.map((option) => enableTypeCoercion(option)));
-    schema = options?.wrap
-      ? "default" in options
-        ? options.wrap(schema, options.default)
-        : options.wrap(schema)
-      : schema;
+    schema = coerce(
+      options?.wrap
+        ? "default" in options
+          ? options.wrap(schema, options.default)
+          : options.wrap(schema)
+        : schema,
+      (output) => coerceString(output),
+    );
   } else if (type.type === "object") {
     const shape = Object.fromEntries(
-      // @ts-ignore
       Object.entries(type.entries).map(([key, def]) => [
         key,
         enableTypeCoercion(def, { cache }),
diff --git a/tests/optional.test.ts b/tests/optional.test.ts
index 192bd00..690e48f 100644
--- a/tests/optional.test.ts
+++ b/tests/optional.test.ts
@@ -26,7 +26,7 @@ describe("optional", () => {
     expect(output1).toMatchObject({ error: {}, value: { name: "default" } });
 
     const schema2 = object({ name: optional(string(), () => default_) });
-    const output2 = parse(createFormData("name", ""), { schema: schema1 });
+    const output2 = parse(createFormData("name", ""), { schema: schema2 });
     expect(output2).toMatchObject({ error: {}, value: { name: "default" } });
   });
 });
diff --git a/tests/pipe.test.ts b/tests/pipe.test.ts
new file mode 100644
index 0000000..e78d655
--- /dev/null
+++ b/tests/pipe.test.ts
@@ -0,0 +1,12 @@
+import { describe, expect, test } from "vitest";
+import { string, object, optional, nullable } from "valibot";
+import { parse } from "../parse";
+import { createFormData } from "./helpers/FormData";
+
+describe("pipe", () => {
+  test("should pass also undefined", () => {
+    const schema = object({ name: optional(nullable(string()), null) });
+    const output = parse(createFormData("name", ""), { schema: schema });
+    expect(output).toMatchObject({ error: {}, value: { name: null } });
+  });
+});