diff --git a/rest/response.go b/rest/response.go
index <HASH>..<HASH> 100644
--- a/rest/response.go
+++ b/rest/response.go
@@ -29,12 +29,17 @@ type ResponseWriter interface {
 	WriteHeader(int)
 }
 
+// This allows to customize the field name used in the error response payload.
+// It defaults to "Error" for compatibility reason, but can be changed before starting the server.
+// eg: rest.ErrorFieldName = "errorMessage"
+var ErrorFieldName = "Error"
+
 // Error produces an error response in JSON with the following structure, '{"Error":"My error message"}'
 // The standard plain text net/http Error helper can still be called like this:
 // http.Error(w, "error message", code)
 func Error(w ResponseWriter, error string, code int) {
 	w.WriteHeader(code)
-	err := w.WriteJson(map[string]string{"Error": error})
+	err := w.WriteJson(map[string]string{ErrorFieldName: error})
 	if err != nil {
 		panic(err)
 	}
Add the ability to customize the field name in the error response.

"Error", capitalized, was not a good choice, but will stay the default
until the next major version (strict compat, see semver.org)
This variable allows the user to customize this field name.