diff --git a/src/errors.h b/src/errors.h
index 26ecf09..85439ba 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -3560,8 +3560,10 @@
 	INIT(= N_("E1402: Using type alias \"%s\" as a String"));
 EXTERN char e_using_typealias_as_value[]
 	INIT(= N_("E1403: Type alias \"%s\" cannot be used as a value"));
+EXTERN char e_abstract_cannot_be_used_in_interface[]
+	INIT(= N_("E1404: Abstract cannot be used in an interface"));
 #endif
-// E1404 - E1499 unused (reserved for Vim9 class support)
+// E1405 - E1499 unused (reserved for Vim9 class support)
 EXTERN char e_cannot_mix_positional_and_non_positional_str[]
 	INIT(= N_("E1500: Cannot mix positional and non-positional arguments: %s"));
 EXTERN char e_fmt_arg_nr_unused_str[]