diff --git a/frontend/dockerfile/builder/build.go b/frontend/dockerfile/builder/build.go
index <HASH>..<HASH> 100644
--- a/frontend/dockerfile/builder/build.go
+++ b/frontend/dockerfile/builder/build.go
@@ -861,6 +861,7 @@ func contextByName(ctx context.Context, c client.Client, sessionID, name string,
 		if err := json.Unmarshal(data, &img); err != nil {
 			return nil, nil, nil, err
 		}
+		img.Created = nil
 
 		st := llb.Image(ref, imgOpt...)
 		st, err = st.WithImageConfig(data)
dockerfile: fix created timestamp

Images built using docker-image:// passed through buildkit named
contexts had the wrong Image.Created timestamp, using the timestamp from
the used image, instead of the current datetime.

To fix, we perform the same input cleanup as in Dockerfile2LLB, and
explicitly set the timestamp to nil.