diff --git a/frontend/dockerfile/docs/reference.md b/frontend/dockerfile/docs/reference.md
index 1028bc00b6ebd..589dc7661f6ba 100644
--- a/frontend/dockerfile/docs/reference.md
+++ b/frontend/dockerfile/docs/reference.md
@@ -1472,6 +1472,10 @@ By default, the `COPY` instruction copies files from the build context. The
 COPY [--from=<stage|image>] <src> ... <dest>
 ```
 
+> **Note**
+>
+> `ONBUILD COPY --from` is not supported.
+
 To copy from a build stage in a
 [multi-stage build](https://docs.docker.com/build/building/multi-stage/),
 specify the name of the stage you want to copy from. You specify stage names