diff --git a/README.md b/README.md
index 4ef3cea..570c77c 100644
--- a/README.md
+++ b/README.md
@@ -59,6 +59,24 @@ curl -X QUERY "http://localhost:3000/v1/validate" -H "Content-Type: application/
 }
 ```
 
+### Example error response
+
+All error responses are returned using the `application/problem+json` media type,
+in accordance with [RFC 9457](https://www.rfc-editor.org/rfc/rfc9457.html).
+
+```http
+HTTP/1.1 400 Bad Request
+Content-Type: application/problem+json
+```
+
+```json
+{
+  "title": "empty body",
+  "detail": "need a body to validate",
+  "status": 400
+}
+```
+
 ## Contributing
 
 Contributing is always appreciated, see [CONTRIBUTING.md](CONTRIBUTING.md).
diff --git a/internal/handlers/validate.go b/internal/handlers/validate.go
index 8d7dcf2..9b467b2 100644
--- a/internal/handlers/validate.go
+++ b/internal/handlers/validate.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/gofiber/fiber/v2"
 	publiccodeParser "github.com/italia/publiccode-parser-go/v5"
+	"github.com/italia/publiccode-validator-api/internal/common"
 )
 
 type PubliccodeymlValidatorHandler struct {
@@ -43,9 +44,7 @@ func (vh *PubliccodeymlValidatorHandler) Query(ctx *fiber.Ctx) error {
 	// }
 
 	if len(ctx.Body()) == 0 {
-		return ctx.Status(fiber.StatusBadRequest).JSON(fiber.Map{
-			"error": "empty body",
-		})
+		return common.Error(fiber.StatusBadRequest, "empty body", "need a body to validate")
 	}
 
 	results := make(publiccodeParser.ValidationResults, 0)