--- a/gondole.go	Thu Apr 13 10:35:42 2017 +0200
+++ b/gondole.go	Thu Apr 13 10:36:18 2017 +0200
@@ -23,6 +23,7 @@
 var (
 	ErrAlreadyRegistered = errors.New("app already registered")
 	ErrEntityNotFound    = errors.New("entity not found")
+	ErrInvalidID         = errors.New("incorrect entity ID")
 )
 
 // prepareRequest insert all pre-defined stuff