diff --git a/src/errors.h b/src/errors.h
index 43baa6a..d1cf4b4 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -3333,4 +3333,6 @@
 	INIT(= N_("E1301: String, Number, List or Blob required for argument %d"));
 EXTERN char e_script_variable_was_deleted[]
 	INIT(= N_("E1302: Script variable was deleted"));
+EXTERN char e_custom_list_completion_function_does_not_return_list_but_str[]
+	INIT(= N_("E1303: Custom list completion function does not return a List but a %s"));
 #endif