diff --git a/scan.go b/scan.go
index 39055bde..57be9882 100644
--- a/scan.go
+++ b/scan.go
@@ -150,6 +150,9 @@ func ReadRR(r io.Reader, file string) (RR, error) {
 // The text "; this is comment" is returned from Comment. Comments inside
 // the RR are returned concatenated along with the RR. Comments on a line
 // by themselves are discarded.
+//
+// Callers should not assume all returned data in an Resource Record is
+// syntactically correct, e.g. illegal base64 in RRSIGs will be returned as-is.
 type ZoneParser struct {
 	c *zlexer