diff --git a/README.md b/README.md
index 94f52e6e..e7a2dc4d 100644
--- a/README.md
+++ b/README.md
@@ -215,8 +215,6 @@ type: `NamingConventionMap` default: `{ enumValues: "change-case-all#pascalCase"
 
 Uses the full path of the enum type as the default value instead of the stringified value.
 
-Note: This option has not been tested with `namingConvention.transformUnderscore` and `namingConvention.typeNames` options and may not work as expected.
-
 Related: https://the-guild.dev/graphql/codegen/docs/config-reference/naming-convention#namingconvention
 
 ### `directives`
diff --git a/src/directive.ts b/src/directive.ts
index d7807149..346620eb 100644
--- a/src/directive.ts
+++ b/src/directive.ts
@@ -1,7 +1,7 @@
 import type { ConstArgumentNode, ConstDirectiveNode, ConstValueNode } from 'graphql';
+import { Kind, valueFromASTUntyped } from 'graphql';
 import type { DirectiveConfig, DirectiveObjectArguments } from './config.js';
 
-import { Kind, valueFromASTUntyped } from 'graphql';
 import { isConvertableRegexp } from './regexp.js';
 
 export interface FormattedDirectiveConfig {
diff --git a/src/graphql.ts b/src/graphql.ts
index d5f6eeca..0738d16e 100644
--- a/src/graphql.ts
+++ b/src/graphql.ts
@@ -5,8 +5,8 @@ import type {
   GraphQLSchema,
   InterfaceTypeDefinitionNode,
   ListTypeNode,
-  NamedTypeNode,
   NameNode,
+  NamedTypeNode,
   NonNullTypeNode,
   ObjectTypeDefinitionNode,
   TypeNode,
diff --git a/src/index.ts b/src/index.ts
index f8ccfd61..c35f789f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,10 +1,10 @@
 import type { PluginFunction, Types } from '@graphql-codegen/plugin-helpers';
 import type { GraphQLSchema } from 'graphql';
+import { transformSchemaAST } from '@graphql-codegen/schema-ast';
+import { buildSchema, printSchema, visit } from 'graphql';
 import type { ValidationSchemaPluginConfig } from './config.js';
 import type { SchemaVisitor } from './types.js';
 
-import { transformSchemaAST } from '@graphql-codegen/schema-ast';
-import { buildSchema, printSchema, visit } from 'graphql';
 import { isGeneratedByIntrospection, topologicalSortAST } from './graphql.js';
 import { MyZodSchemaVisitor } from './myzod/index.js';
 import { ValibotSchemaVisitor } from './valibot/index.js';
diff --git a/src/myzod/index.ts b/src/myzod/index.ts
index 8804a153..f06a23c0 100644
--- a/src/myzod/index.ts
+++ b/src/myzod/index.ts
@@ -10,23 +10,23 @@ import type {
   TypeNode,
   UnionTypeDefinitionNode,
 } from 'graphql';
-import type { ValidationSchemaPluginConfig } from '../config.js';
-import type { Visitor } from '../visitor.js';
 
 import { resolveExternalModuleAndFn } from '@graphql-codegen/plugin-helpers';
-import { convertNameParts, DeclarationBlock, indent } from '@graphql-codegen/visitor-plugin-common';
+import { DeclarationBlock, convertNameParts, indent } from '@graphql-codegen/visitor-plugin-common';
 import {
   Kind,
 } from 'graphql';
+import type { Visitor } from '../visitor.js';
+import type { ValidationSchemaPluginConfig } from '../config.js';
 import { buildApi, formatDirectiveConfig } from '../directive.js';
 import {
-  escapeGraphQLCharacters,
   InterfaceTypeDefinitionBuilder,
+  ObjectTypeDefinitionBuilder,
+  escapeGraphQLCharacters,
   isInput,
   isListType,
   isNamedType,
   isNonNullType,
-  ObjectTypeDefinitionBuilder,
 } from '../graphql.js';
 import { BaseSchemaVisitor } from '../schema_visitor.js';
 
@@ -290,10 +290,10 @@ function generateFieldTypeMyZodSchema(config: ValidationSchemaPluginConfig, visi
 
       if (defaultValue?.kind === Kind.STRING || defaultValue?.kind === Kind.ENUM) {
         if (config.useEnumTypeAsDefaultValue && defaultValue?.kind !== Kind.STRING) {
-          let value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn('change-case-all#pascalCase'));
+          let value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn('change-case-all#pascalCase'), config?.namingConvention?.transformUnderscore);
 
           if (config.namingConvention?.enumValues)
-            value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn(config.namingConvention?.enumValues));
+            value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn(config.namingConvention?.enumValues), config?.namingConvention?.transformUnderscore);
 
           appliedDirectivesGen = `${appliedDirectivesGen}.default(${visitor.convertName(type.name.value)}.${value})`;
         }
diff --git a/src/valibot/index.ts b/src/valibot/index.ts
index 71c4d09b..c05c1316 100644
--- a/src/valibot/index.ts
+++ b/src/valibot/index.ts
@@ -10,18 +10,18 @@ import type {
   TypeNode,
   UnionTypeDefinitionNode,
 } from 'graphql';
+import { DeclarationBlock, indent } from '@graphql-codegen/visitor-plugin-common';
 import type { ValidationSchemaPluginConfig } from '../config.js';
 
 import type { Visitor } from '../visitor.js';
-import { DeclarationBlock, indent } from '@graphql-codegen/visitor-plugin-common';
 import { buildApiForValibot, formatDirectiveConfig } from '../directive.js';
 import {
   InterfaceTypeDefinitionBuilder,
+  ObjectTypeDefinitionBuilder,
   isInput,
   isListType,
   isNamedType,
   isNonNullType,
-  ObjectTypeDefinitionBuilder,
 } from '../graphql.js';
 import { BaseSchemaVisitor } from '../schema_visitor.js';
 
diff --git a/src/visitor.ts b/src/visitor.ts
index 7866d2a1..5666a3d2 100644
--- a/src/visitor.ts
+++ b/src/visitor.ts
@@ -5,12 +5,12 @@ import type {
   NameNode,
   ObjectTypeDefinitionNode,
 } from 'graphql';
-import type { ValidationSchemaPluginConfig } from './config.js';
 import { TsVisitor } from '@graphql-codegen/typescript';
 
 import {
   specifiedScalarTypes,
 } from 'graphql';
+import type { ValidationSchemaPluginConfig } from './config.js';
 
 export class Visitor extends TsVisitor {
   constructor(
diff --git a/src/yup/index.ts b/src/yup/index.ts
index b1805d8a..56d71d17 100644
--- a/src/yup/index.ts
+++ b/src/yup/index.ts
@@ -10,23 +10,23 @@ import type {
   TypeNode,
   UnionTypeDefinitionNode,
 } from 'graphql';
-import type { ValidationSchemaPluginConfig } from '../config.js';
-import type { Visitor } from '../visitor.js';
 
 import { resolveExternalModuleAndFn } from '@graphql-codegen/plugin-helpers';
-import { convertNameParts, DeclarationBlock, indent } from '@graphql-codegen/visitor-plugin-common';
+import { DeclarationBlock, convertNameParts, indent } from '@graphql-codegen/visitor-plugin-common';
 import {
   Kind,
 } from 'graphql';
+import type { Visitor } from '../visitor.js';
+import type { ValidationSchemaPluginConfig } from '../config.js';
 import { buildApi, formatDirectiveConfig } from '../directive.js';
 import {
-  escapeGraphQLCharacters,
   InterfaceTypeDefinitionBuilder,
+  ObjectTypeDefinitionBuilder,
+  escapeGraphQLCharacters,
   isInput,
   isListType,
   isNamedType,
   isNonNullType,
-  ObjectTypeDefinitionBuilder,
 } from '../graphql.js';
 import { BaseSchemaVisitor } from '../schema_visitor.js';
 
@@ -292,10 +292,10 @@ function shapeFields(fields: readonly (FieldDefinitionNode | InputValueDefinitio
 
         if (defaultValue?.kind === Kind.STRING || defaultValue?.kind === Kind.ENUM) {
           if (config.useEnumTypeAsDefaultValue && defaultValue?.kind !== Kind.STRING) {
-            let value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn('change-case-all#pascalCase'));
+            let value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn('change-case-all#pascalCase'), config?.namingConvention?.transformUnderscore);
 
             if (config.namingConvention?.enumValues)
-              value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn(config.namingConvention?.enumValues));
+              value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn(config.namingConvention?.enumValues), config?.namingConvention?.transformUnderscore);
 
             fieldSchema = `${fieldSchema}.default(${visitor.convertName(field.name.value)}.${value})`;
           }
diff --git a/src/zod/index.ts b/src/zod/index.ts
index b1164fb0..4c9a77a5 100644
--- a/src/zod/index.ts
+++ b/src/zod/index.ts
@@ -10,23 +10,23 @@ import type {
   TypeNode,
   UnionTypeDefinitionNode,
 } from 'graphql';
-import type { ValidationSchemaPluginConfig } from '../config.js';
-import type { Visitor } from '../visitor.js';
 
 import { resolveExternalModuleAndFn } from '@graphql-codegen/plugin-helpers';
-import { convertNameParts, DeclarationBlock, indent } from '@graphql-codegen/visitor-plugin-common';
+import { DeclarationBlock, convertNameParts, indent } from '@graphql-codegen/visitor-plugin-common';
 import {
   Kind,
 } from 'graphql';
+import type { Visitor } from '../visitor.js';
+import type { ValidationSchemaPluginConfig } from '../config.js';
 import { buildApi, formatDirectiveConfig } from '../directive.js';
 import {
-  escapeGraphQLCharacters,
   InterfaceTypeDefinitionBuilder,
+  ObjectTypeDefinitionBuilder,
+  escapeGraphQLCharacters,
   isInput,
   isListType,
   isNamedType,
   isNonNullType,
-  ObjectTypeDefinitionBuilder,
 } from '../graphql.js';
 import { BaseSchemaVisitor } from '../schema_visitor.js';
 
@@ -306,10 +306,10 @@ function generateFieldTypeZodSchema(config: ValidationSchemaPluginConfig, visito
 
       if (defaultValue?.kind === Kind.STRING || defaultValue?.kind === Kind.ENUM) {
         if (config.useEnumTypeAsDefaultValue && defaultValue?.kind !== Kind.STRING) {
-          let value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn('change-case-all#pascalCase'));
+          let value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn('change-case-all#pascalCase'), config.namingConvention?.transformUnderscore);
 
           if (config.namingConvention?.enumValues)
-            value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn(config.namingConvention?.enumValues));
+            value = convertNameParts(defaultValue.value, resolveExternalModuleAndFn(config.namingConvention?.enumValues), config.namingConvention?.transformUnderscore);
 
           appliedDirectivesGen = `${appliedDirectivesGen}.default(${type.name.value}.${value})`;
         }
diff --git a/tests/directive.spec.ts b/tests/directive.spec.ts
index 1fa8036a..2ac9c6c2 100644
--- a/tests/directive.spec.ts
+++ b/tests/directive.spec.ts
@@ -1,4 +1,5 @@
 import type { ConstArgumentNode, ConstDirectiveNode, ConstValueNode, NameNode } from 'graphql';
+import { Kind, parseConstValue } from 'graphql';
 import type { DirectiveConfig, DirectiveObjectArguments } from '../src/config';
 
 import type {
@@ -6,7 +7,6 @@ import type {
   FormattedDirectiveConfig,
   FormattedDirectiveObjectArguments,
 } from '../src/directive';
-import { Kind, parseConstValue } from 'graphql';
 import {
   buildApi,
   buildApiForValibot,
diff --git a/tests/graphql.spec.ts b/tests/graphql.spec.ts
index 87e90b87..92aae319 100644
--- a/tests/graphql.spec.ts
+++ b/tests/graphql.spec.ts
@@ -3,16 +3,16 @@ import type {
 } from 'graphql';
 import { Graph } from 'graphlib';
 import {
+  Kind,
   buildClientSchema,
   buildSchema,
   introspectionFromSchema,
-  Kind,
   parse,
   print,
 } from 'graphql';
 import dedent from 'ts-dedent';
 
-import { escapeGraphQLCharacters, isGeneratedByIntrospection, ObjectTypeDefinitionBuilder, topologicalSortAST, topsort } from '../src/graphql';
+import { ObjectTypeDefinitionBuilder, escapeGraphQLCharacters, isGeneratedByIntrospection, topologicalSortAST, topsort } from '../src/graphql';
 
 describe('graphql', () => {
   describe('objectTypeDefinitionBuilder', () => {
diff --git a/tests/myzod.spec.ts b/tests/myzod.spec.ts
index 0497476e..23d073a8 100644
--- a/tests/myzod.spec.ts
+++ b/tests/myzod.spec.ts
@@ -1444,4 +1444,77 @@ describe('myzod', () => {
     expect(result.content).toContain('ratio: myzod.number().default(0.5).optional().nullable()');
     expect(result.content).toContain('isMember: myzod.boolean().default(true).optional().nullable()');
   });
+
+  it('with default input values as enum types with underscores', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      enum PageType {
+        PUBLIC
+        BASIC_AUTH
+      }
+      input PageInput {
+        pageType: PageType! = BASIC_AUTH
+        greeting: String = "Hello"
+        score: Int = 100
+        ratio: Float = 0.5
+        isMember: Boolean = true
+      }
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'myzod',
+        importFrom: './types',
+        useEnumTypeAsDefaultValue: true,
+      },
+      {},
+    );
+
+    expect(result.content).toContain('export const PageTypeSchema = myzod.enum(PageType)');
+    expect(result.content).toContain('export function PageInputSchema(): myzod.Type<PageInput>');
+
+    expect(result.content).toContain('pageType: PageTypeSchema.default(PageType.Basic_Auth)');
+    expect(result.content).toContain('greeting: myzod.string().default("Hello").optional().nullable()');
+    expect(result.content).toContain('score: myzod.number().default(100).optional().nullable()');
+    expect(result.content).toContain('ratio: myzod.number().default(0.5).optional().nullable()');
+    expect(result.content).toContain('isMember: myzod.boolean().default(true).optional().nullable()');
+  });
+
+  it('with default input values as enum types with no underscores', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      enum PageType {
+        PUBLIC
+        BASIC_AUTH
+      }
+      input PageInput {
+        pageType: PageType! = BASIC_AUTH
+        greeting: String = "Hello"
+        score: Int = 100
+        ratio: Float = 0.5
+        isMember: Boolean = true
+      }
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'myzod',
+        importFrom: './types',
+        useEnumTypeAsDefaultValue: true,
+        namingConvention: {
+          transformUnderscore: true,
+        },
+      },
+      {},
+    );
+
+    expect(result.content).toContain('export const PageTypeSchema = myzod.enum(PageType)');
+    expect(result.content).toContain('export function PageInputSchema(): myzod.Type<PageInput>');
+
+    expect(result.content).toContain('pageType: PageTypeSchema.default(PageType.BasicAuth)');
+    expect(result.content).toContain('greeting: myzod.string().default("Hello").optional().nullable()');
+    expect(result.content).toContain('score: myzod.number().default(100).optional().nullable()');
+    expect(result.content).toContain('ratio: myzod.number().default(0.5).optional().nullable()');
+    expect(result.content).toContain('isMember: myzod.boolean().default(true).optional().nullable()');
+  });
 });
diff --git a/tests/yup.spec.ts b/tests/yup.spec.ts
index bad9c1f4..1b7d010c 100644
--- a/tests/yup.spec.ts
+++ b/tests/yup.spec.ts
@@ -1470,4 +1470,81 @@ describe('yup', () => {
     expect(result.content).toContain('ratio: yup.number().defined().nullable().default(0.5).optional()');
     expect(result.content).toContain('isMember: yup.boolean().defined().nullable().default(true).optional()');
   });
+
+  it('with default input values as enum types with underscores', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      enum PageType {
+        PUBLIC
+        BASIC_AUTH
+      }
+      input PageInput {
+        pageType: PageType! = BASIC_AUTH
+        greeting: String = "Hello"
+        score: Int = 100
+        ratio: Float = 0.5
+        isMember: Boolean = true
+      }
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'yup',
+        importFrom: './types',
+        useEnumTypeAsDefaultValue: true,
+      },
+      {},
+    );
+
+    expect(result.content).toContain(
+      'export const PageTypeSchema = yup.string<PageType>().oneOf(Object.values(PageType)).defined()',
+    );
+    expect(result.content).toContain('export function PageInputSchema(): yup.ObjectSchema<PageInput>');
+
+    expect(result.content).toContain('pageType: PageTypeSchema.nonNullable().default(PageType.Basic_Auth)');
+    expect(result.content).toContain('greeting: yup.string().defined().nullable().default("Hello").optional()');
+    expect(result.content).toContain('score: yup.number().defined().nullable().default(100).optional()');
+    expect(result.content).toContain('ratio: yup.number().defined().nullable().default(0.5).optional()');
+    expect(result.content).toContain('isMember: yup.boolean().defined().nullable().default(true).optional()');
+  });
+
+  it('with default input values as enum types with no underscores', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      enum PageType {
+        PUBLIC
+        BASIC_AUTH
+      }
+      input PageInput {
+        pageType: PageType! = BASIC_AUTH
+        greeting: String = "Hello"
+        score: Int = 100
+        ratio: Float = 0.5
+        isMember: Boolean = true
+      }
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'yup',
+        importFrom: './types',
+        useEnumTypeAsDefaultValue: true,
+        namingConvention: {
+          transformUnderscore: true,
+        },
+      },
+      {},
+    );
+
+    expect(result.content).toContain(
+      'export const PageTypeSchema = yup.string<PageType>().oneOf(Object.values(PageType)).defined()',
+    );
+    expect(result.content).toContain('export function PageInputSchema(): yup.ObjectSchema<PageInput>');
+
+    expect(result.content).toContain('pageType: PageTypeSchema.nonNullable().default(PageType.BasicAuth)');
+    expect(result.content).toContain('greeting: yup.string().defined().nullable().default("Hello").optional()');
+    expect(result.content).toContain('score: yup.number().defined().nullable().default(100).optional()');
+    expect(result.content).toContain('ratio: yup.number().defined().nullable().default(0.5).optional()');
+    expect(result.content).toContain('isMember: yup.boolean().defined().nullable().default(true).optional()');
+  });
 });
diff --git a/tests/zod.spec.ts b/tests/zod.spec.ts
index 28cbe369..8e58db69 100644
--- a/tests/zod.spec.ts
+++ b/tests/zod.spec.ts
@@ -566,6 +566,81 @@ describe('zod', () => {
     expect(result.content).toContain('isMember: z.boolean().default(true).nullish()');
   });
 
+  it('with default input values as enum types with underscores', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      enum PageType {
+        BASIC_AUTH
+        PUBLIC
+      }
+      input PageInput {
+        pageType: PageType! = BASIC_AUTH
+        greeting: String = "Hello"
+        score: Int = 100
+        ratio: Float = 0.5
+        isMember: Boolean = true
+      }
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'zod',
+        importFrom: './types',
+        useEnumTypeAsDefaultValue: true,
+      },
+      {
+      },
+    );
+
+    expect(result.content).toContain('export const PageTypeSchema = z.nativeEnum(PageType)');
+    expect(result.content).toContain('export function PageInputSchema(): z.ZodObject<Properties<PageInput>>');
+
+    expect(result.content).toContain('pageType: PageTypeSchema.default(PageType.Basic_Auth)');
+    expect(result.content).toContain('greeting: z.string().default("Hello").nullish()');
+    expect(result.content).toContain('score: z.number().default(100).nullish()');
+    expect(result.content).toContain('ratio: z.number().default(0.5).nullish()');
+    expect(result.content).toContain('isMember: z.boolean().default(true).nullish()');
+  });
+
+  it('with default input values as enum types with no underscores', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      enum PageType {
+        BASIC_AUTH
+        PUBLIC
+      }
+      input PageInput {
+        pageType: PageType! = BASIC_AUTH
+        greeting: String = "Hello"
+        score: Int = 100
+        ratio: Float = 0.5
+        isMember: Boolean = true
+      }
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'zod',
+        importFrom: './types',
+        useEnumTypeAsDefaultValue: true,
+        namingConvention: {
+          transformUnderscore: true,
+        },
+      },
+      {
+      },
+    );
+
+    expect(result.content).toContain('export const PageTypeSchema = z.nativeEnum(PageType)');
+    expect(result.content).toContain('export function PageInputSchema(): z.ZodObject<Properties<PageInput>>');
+
+    expect(result.content).toContain('pageType: PageTypeSchema.default(PageType.BasicAuth)');
+    expect(result.content).toContain('greeting: z.string().default("Hello").nullish()');
+    expect(result.content).toContain('score: z.number().default(100).nullish()');
+    expect(result.content).toContain('ratio: z.number().default(0.5).nullish()');
+    expect(result.content).toContain('isMember: z.boolean().default(true).nullish()');
+  });
+
   it('with default input values', async () => {
     const schema = buildSchema(/* GraphQL */ `
       enum PageType {