diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 8bd47ee4bb..962ba1df35 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -102,8 +102,8 @@ struct Visitor
     /* Must be set to visit explicit null values.  */
     void (*type_null)(Visitor *v, const char *name, Error **errp);
 
-    /* Must be set for input visitors, optional otherwise.  The core
-     * takes care of the return type in the public interface. */
+    /* Must be set for input visitors to visit structs, optional otherwise.
+       The core takes care of the return type in the public interface. */
     void (*optional)(Visitor *v, const char *name, bool *present);
 
     /* Must be set */
diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c
index 8dfa561252..1a855c5474 100644
--- a/qapi/string-input-visitor.c
+++ b/qapi/string-input-visitor.c
@@ -314,18 +314,6 @@ static void parse_type_number(Visitor *v, const char *name, double *obj,
     *obj = val;
 }
 
-static void parse_optional(Visitor *v, const char *name, bool *present)
-{
-    StringInputVisitor *siv = to_siv(v);
-
-    if (!siv->string) {
-        *present = false;
-        return;
-    }
-
-    *present = true;
-}
-
 static void string_input_free(Visitor *v)
 {
     StringInputVisitor *siv = to_siv(v);
@@ -351,7 +339,6 @@ Visitor *string_input_visitor_new(const char *str)
     v->visitor.start_list = start_list;
     v->visitor.next_list = next_list;
     v->visitor.end_list = end_list;
-    v->visitor.optional = parse_optional;
     v->visitor.free = string_input_free;
 
     v->string = str;