diff --git a/src/libsystemd/sd-varlink/sd-varlink-idl.c b/src/libsystemd/sd-varlink/sd-varlink-idl.c
index 144450b702..22b6026a01 100644
--- a/src/libsystemd/sd-varlink/sd-varlink-idl.c
+++ b/src/libsystemd/sd-varlink/sd-varlink-idl.c
@@ -387,7 +387,10 @@ static int varlink_idl_format_symbol(
 
                 /* Sooner or later we want to export this in a proper IDL language construct, see
                  * https://github.com/varlink/varlink.github.io/issues/26 – but for now export this as a
-                 * comment. */
+                 * comment.
+                 *
+                 * Until this is resolved upsteam, consider this comment part of the API (i.e. don't change
+                 * only extend). It is used by tools like varlink-http-bridge. */
                 if ((symbol->symbol_flags & (SD_VARLINK_REQUIRES_MORE|SD_VARLINK_SUPPORTS_MORE)) != 0) {
                         fputs(colors[COLOR_COMMENT], f);
                         if (FLAGS_SET(symbol->symbol_flags, SD_VARLINK_REQUIRES_MORE))