diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go
index 98102291ab8..3b398c9fc32 100644
--- a/src/encoding/json/decode.go
+++ b/src/encoding/json/decode.go
@@ -113,9 +113,6 @@ func Unmarshal(data []byte, v any) error {
 // The input can be assumed to be a valid encoding of
 // a JSON value. UnmarshalJSON must copy the JSON data
 // if it wishes to retain the data after returning.
-//
-// By convention, to approximate the behavior of [Unmarshal] itself,
-// Unmarshalers implement UnmarshalJSON([]byte("null")) as a no-op.
 type Unmarshaler interface {
 	UnmarshalJSON([]byte) error
 }