diff --git a/captcha.go b/captcha.go
index d4468dd..2bb489a 100644
--- a/captcha.go
+++ b/captcha.go
@@ -9,5 +9,5 @@ import (
 type Captcha interface {
 	HttpMiddleware(container *do.Injector) func(next http.Handler) http.Handler
 	Verify(answer, salt string, clear bool) error
-	Generate(captchaUuid string, u User) (answer, salt string)
+	Generate(captchaUuid string, u User) (answer, salt string, err error)
 }