diff --git a/internal/test/issue-vnd-json/config.yaml b/internal/test/issue-vnd-json/config.yaml
new file mode 100644
index 000000000..0739b2b4f
--- /dev/null
+++ b/internal/test/issue-vnd-json/config.yaml
@@ -0,0 +1,6 @@
+# yaml-language-server: $schema=../../../configuration-schema.json
+package: issuevndjson
+output: schema.gen.go
+generate:
+  models: true
+  client: true
diff --git a/internal/test/issue-vnd-json/doc.go b/internal/test/issue-vnd-json/doc.go
new file mode 100644
index 000000000..fc16b3991
--- /dev/null
+++ b/internal/test/issue-vnd-json/doc.go
@@ -0,0 +1,3 @@
+package issuevndjson
+
+//go:generate go run github.com/oapi-codegen/oapi-codegen/v2/cmd/oapi-codegen --config=config.yaml spec.yaml
diff --git a/internal/test/issue-vnd-json/schema.gen.go b/internal/test/issue-vnd-json/schema.gen.go
new file mode 100644
index 000000000..e8433e97e
--- /dev/null
+++ b/internal/test/issue-vnd-json/schema.gen.go
@@ -0,0 +1,358 @@
+// Package issuevndjson provides primitives to interact with the openapi HTTP API.
+//
+// Code generated by github.com/oapi-codegen/oapi-codegen/v2 version v2.0.0-00010101000000-000000000000 DO NOT EDIT.
+package issuevndjson
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/oapi-codegen/runtime"
+)
+
+// ErrorA defines model for error_a.
+type ErrorA struct {
+	Message *string `json:"message,omitempty"`
+}
+
+// ErrorB defines model for error_b.
+type ErrorB struct {
+	Code *int `json:"code,omitempty"`
+}
+
+// Item defines model for item.
+type Item struct {
+	Id *string `json:"id,omitempty"`
+}
+
+// CreateItem422ApplicationVndAPIPlusJSONResponseBody defines parameters for CreateItem.
+type CreateItem422ApplicationVndAPIPlusJSONResponseBody struct {
+	union json.RawMessage
+}
+
+// AsErrorA returns the union data inside the CreateItem422ApplicationVndAPIPlusJSONResponseBody as a ErrorA
+func (t CreateItem422ApplicationVndAPIPlusJSONResponseBody) AsErrorA() (ErrorA, error) {
+	var body ErrorA
+	err := json.Unmarshal(t.union, &body)
+	return body, err
+}
+
+// FromErrorA overwrites any union data inside the CreateItem422ApplicationVndAPIPlusJSONResponseBody as the provided ErrorA
+func (t *CreateItem422ApplicationVndAPIPlusJSONResponseBody) FromErrorA(v ErrorA) error {
+	b, err := json.Marshal(v)
+	t.union = b
+	return err
+}
+
+// MergeErrorA performs a merge with any union data inside the CreateItem422ApplicationVndAPIPlusJSONResponseBody, using the provided ErrorA
+func (t *CreateItem422ApplicationVndAPIPlusJSONResponseBody) MergeErrorA(v ErrorA) error {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return err
+	}
+
+	merged, err := runtime.JSONMerge(t.union, b)
+	t.union = merged
+	return err
+}
+
+// AsErrorB returns the union data inside the CreateItem422ApplicationVndAPIPlusJSONResponseBody as a ErrorB
+func (t CreateItem422ApplicationVndAPIPlusJSONResponseBody) AsErrorB() (ErrorB, error) {
+	var body ErrorB
+	err := json.Unmarshal(t.union, &body)
+	return body, err
+}
+
+// FromErrorB overwrites any union data inside the CreateItem422ApplicationVndAPIPlusJSONResponseBody as the provided ErrorB
+func (t *CreateItem422ApplicationVndAPIPlusJSONResponseBody) FromErrorB(v ErrorB) error {
+	b, err := json.Marshal(v)
+	t.union = b
+	return err
+}
+
+// MergeErrorB performs a merge with any union data inside the CreateItem422ApplicationVndAPIPlusJSONResponseBody, using the provided ErrorB
+func (t *CreateItem422ApplicationVndAPIPlusJSONResponseBody) MergeErrorB(v ErrorB) error {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return err
+	}
+
+	merged, err := runtime.JSONMerge(t.union, b)
+	t.union = merged
+	return err
+}
+
+func (t CreateItem422ApplicationVndAPIPlusJSONResponseBody) MarshalJSON() ([]byte, error) {
+	b, err := t.union.MarshalJSON()
+	return b, err
+}
+
+func (t *CreateItem422ApplicationVndAPIPlusJSONResponseBody) UnmarshalJSON(b []byte) error {
+	err := t.union.UnmarshalJSON(b)
+	return err
+}
+
+// RequestEditorFn is the function signature for the RequestEditor callback function
+type RequestEditorFn func(ctx context.Context, req *http.Request) error
+
+// Doer performs HTTP requests.
+//
+// The standard http.Client implements this interface.
+type HttpRequestDoer interface {
+	Do(req *http.Request) (*http.Response, error)
+}
+
+// Client which conforms to the OpenAPI3 specification for this service.
+type Client struct {
+	// The endpoint of the server conforming to this interface, with scheme,
+	// https://api.deepmap.com for example. This can contain a path relative
+	// to the server, such as https://api.deepmap.com/dev-test, and all the
+	// paths in the swagger spec will be appended to the server.
+	Server string
+
+	// Doer for performing requests, typically a *http.Client with any
+	// customized settings, such as certificate chains.
+	Client HttpRequestDoer
+
+	// A list of callbacks for modifying requests which are generated before sending over
+	// the network.
+	RequestEditors []RequestEditorFn
+}
+
+// ClientOption allows setting custom parameters during construction
+type ClientOption func(*Client) error
+
+// Creates a new Client, with reasonable defaults
+func NewClient(server string, opts ...ClientOption) (*Client, error) {
+	// create a client with sane default values
+	client := Client{
+		Server: server,
+	}
+	// mutate client and add all optional params
+	for _, o := range opts {
+		if err := o(&client); err != nil {
+			return nil, err
+		}
+	}
+	// ensure the server URL always has a trailing slash
+	if !strings.HasSuffix(client.Server, "/") {
+		client.Server += "/"
+	}
+	// create httpClient, if not already present
+	if client.Client == nil {
+		client.Client = &http.Client{}
+	}
+	return &client, nil
+}
+
+// WithHTTPClient allows overriding the default Doer, which is
+// automatically created using http.Client. This is useful for tests.
+func WithHTTPClient(doer HttpRequestDoer) ClientOption {
+	return func(c *Client) error {
+		c.Client = doer
+		return nil
+	}
+}
+
+// WithRequestEditorFn allows setting up a callback function, which will be
+// called right before sending the request. This can be used to mutate the request.
+func WithRequestEditorFn(fn RequestEditorFn) ClientOption {
+	return func(c *Client) error {
+		c.RequestEditors = append(c.RequestEditors, fn)
+		return nil
+	}
+}
+
+// The interface specification for the client above.
+type ClientInterface interface {
+
+	// CreateItem performs a POST /items (the `CreateItem` operationId) request.
+	CreateItem(ctx context.Context, reqEditors ...RequestEditorFn) (*http.Response, error)
+}
+
+// CreateItem performs a POST /items (the `CreateItem` operationId) request.
+func (c *Client) CreateItem(ctx context.Context, reqEditors ...RequestEditorFn) (*http.Response, error) {
+	req, err := NewCreateItemRequest(c.Server)
+	if err != nil {
+		return nil, err
+	}
+	req = req.WithContext(ctx)
+	if err := c.applyEditors(ctx, req, reqEditors); err != nil {
+		return nil, err
+	}
+	return c.Client.Do(req)
+}
+
+// NewCreateItemRequest constructs an http.Request for the CreateItem method
+func NewCreateItemRequest(server string) (*http.Request, error) {
+	var err error
+
+	serverURL, err := url.Parse(server)
+	if err != nil {
+		return nil, err
+	}
+
+	operationPath := fmt.Sprintf("/items")
+	if operationPath[0] == '/' {
+		operationPath = "." + operationPath
+	}
+
+	queryURL, err := serverURL.Parse(operationPath)
+	if err != nil {
+		return nil, err
+	}
+
+	req, err := http.NewRequest(http.MethodPost, queryURL.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return req, nil
+}
+
+func (c *Client) applyEditors(ctx context.Context, req *http.Request, additionalEditors []RequestEditorFn) error {
+	for _, r := range c.RequestEditors {
+		if err := r(ctx, req); err != nil {
+			return err
+		}
+	}
+	for _, r := range additionalEditors {
+		if err := r(ctx, req); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// ClientWithResponses builds on ClientInterface to offer response payloads
+type ClientWithResponses struct {
+	ClientInterface
+}
+
+// NewClientWithResponses creates a new ClientWithResponses, which wraps
+// Client with return type handling
+func NewClientWithResponses(server string, opts ...ClientOption) (*ClientWithResponses, error) {
+	client, err := NewClient(server, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return &ClientWithResponses{client}, nil
+}
+
+// WithBaseURL overrides the baseURL.
+func WithBaseURL(baseURL string) ClientOption {
+	return func(c *Client) error {
+		newBaseURL, err := url.Parse(baseURL)
+		if err != nil {
+			return err
+		}
+		c.Server = newBaseURL.String()
+		return nil
+	}
+}
+
+// ClientWithResponsesInterface is the interface specification for the client with responses above.
+type ClientWithResponsesInterface interface {
+
+	// CreateItemWithResponse performs a POST /items (the `CreateItem` operationId) request.
+	//
+	// Returns a wrapper object for the known response body format(s).
+	CreateItemWithResponse(ctx context.Context, reqEditors ...RequestEditorFn) (*CreateItemResponse, error)
+}
+
+type CreateItemResponse struct {
+	Body         []byte
+	HTTPResponse *http.Response
+	// ApplicationvndApiJSON200 the response for an HTTP 200 `application/vnd.api+json` response
+	ApplicationvndApiJSON200 *Item
+	// ApplicationvndApiJSON422 the response for an HTTP 422 `application/vnd.api+json` response
+	ApplicationvndApiJSON422 *CreateItem422ApplicationVndAPIPlusJSONResponseBody
+}
+
+// GetApplicationvndApiJSON200 returns the response for an HTTP 200 `application/vnd.api+json` response
+func (r CreateItemResponse) GetApplicationvndApiJSON200() *Item {
+	return r.ApplicationvndApiJSON200
+}
+
+// GetApplicationvndApiJSON422 returns the response for an HTTP 422 `application/vnd.api+json` response
+func (r CreateItemResponse) GetApplicationvndApiJSON422() *CreateItem422ApplicationVndAPIPlusJSONResponseBody {
+	return r.ApplicationvndApiJSON422
+}
+
+// GetBody returns the raw response body bytes
+func (r CreateItemResponse) GetBody() []byte {
+	return r.Body
+}
+
+// Status returns HTTPResponse.Status
+func (r CreateItemResponse) Status() string {
+	if r.HTTPResponse != nil {
+		return r.HTTPResponse.Status
+	}
+	return http.StatusText(0)
+}
+
+// StatusCode returns HTTPResponse.StatusCode
+func (r CreateItemResponse) StatusCode() int {
+	if r.HTTPResponse != nil {
+		return r.HTTPResponse.StatusCode
+	}
+	return 0
+}
+
+// ContentType is a convenience method to retrieve the Content-Type value from the HTTP response headers
+func (r CreateItemResponse) ContentType() string {
+	if r.HTTPResponse != nil {
+		return r.HTTPResponse.Header.Get("Content-Type")
+	}
+	return ""
+}
+
+// CreateItemWithResponse performs a POST /items (the `CreateItem` operationId) request.
+//
+// Returns a wrapper object for the known response body format(s).
+func (c *ClientWithResponses) CreateItemWithResponse(ctx context.Context, reqEditors ...RequestEditorFn) (*CreateItemResponse, error) {
+	rsp, err := c.CreateItem(ctx, reqEditors...)
+	if err != nil {
+		return nil, err
+	}
+	return ParseCreateItemResponse(rsp)
+}
+
+// ParseCreateItemResponse parses an HTTP response from a CreateItemWithResponse call
+func ParseCreateItemResponse(rsp *http.Response) (*CreateItemResponse, error) {
+	bodyBytes, err := io.ReadAll(rsp.Body)
+	defer func() { _ = rsp.Body.Close() }()
+	if err != nil {
+		return nil, err
+	}
+
+	response := &CreateItemResponse{
+		Body:         bodyBytes,
+		HTTPResponse: rsp,
+	}
+
+	switch {
+	case strings.Contains(rsp.Header.Get("Content-Type"), "json") && rsp.StatusCode == 200:
+		var dest Item
+		if err := json.Unmarshal(bodyBytes, &dest); err != nil {
+			return nil, err
+		}
+		response.ApplicationvndApiJSON200 = &dest
+
+	case strings.Contains(rsp.Header.Get("Content-Type"), "json") && rsp.StatusCode == 422:
+		var dest CreateItem422ApplicationVndAPIPlusJSONResponseBody
+		if err := json.Unmarshal(bodyBytes, &dest); err != nil {
+			return nil, err
+		}
+		response.ApplicationvndApiJSON422 = &dest
+
+	}
+
+	return response, nil
+}
diff --git a/internal/test/issue-vnd-json/spec.yaml b/internal/test/issue-vnd-json/spec.yaml
new file mode 100644
index 000000000..b55ecb7d8
--- /dev/null
+++ b/internal/test/issue-vnd-json/spec.yaml
@@ -0,0 +1,38 @@
+openapi: "3.0.0"
+info:
+  title: rootly-go issue with
+  version: "1.0.0"
+paths:
+  /items:
+    post:
+      operationId: createItem
+      responses:
+        "200":
+          content:
+            application/vnd.api+json:
+              schema:
+                $ref: "#/components/schemas/item"
+        "422":
+          content:
+            application/vnd.api+json:
+              schema:
+                anyOf:
+                  - $ref: "#/components/schemas/error_a"
+                  - $ref: "#/components/schemas/error_b"
+components:
+  schemas:
+    item:
+      type: object
+      properties:
+        id:
+          type: string
+    error_a:
+      type: object
+      properties:
+        message:
+          type: string
+    error_b:
+      type: object
+      properties:
+        code:
+          type: integer
diff --git a/pkg/codegen/operations.go b/pkg/codegen/operations.go
index 2bea1e4a8..cf219c2f2 100644
--- a/pkg/codegen/operations.go
+++ b/pkg/codegen/operations.go
@@ -558,7 +558,7 @@ func (o *OperationDefinition) GetResponseTypeDefinitions() ([]ResponseTypeDefini
 						baseTypeName := fmt.Sprintf("%s%s", nameNormalizer(contentTypeName), nameNormalizer(responseName))
 
 						typeName = strings.ReplaceAll(baseTypeName, "Json", "JSON")
-						tag = strings.ReplaceAll(nameNormalizer(contentTypeName), "Json", "JSON")
+						tag = mediaTypeToCamelCase(contentTypeName)
 					// YAML:
 					case slices.Contains(contentTypesYAML, contentTypeName):
 						typeName = fmt.Sprintf("YAML%s", nameNormalizer(responseName))
@@ -860,13 +860,13 @@ func (r ResponseContentDefinition) IsStreamingContentType() bool {
 }
 
 type ResponseHeaderDefinition struct {
-	Name               string
-	GoName             string
-	Schema             Schema
-	Required           bool
-	Nullable           bool
-	Deprecated         bool
-	DeprecationReason  string
+	Name              string
+	GoName            string
+	Schema            Schema
+	Required          bool
+	Nullable          bool
+	Deprecated        bool
+	DeprecationReason string
 }
 
 // DeprecationComment returns a Go-style deprecation comment if the header is deprecated, otherwise returns an empty string.