diff --git a/manifest/schema2/builder.go b/manifest/schema2/builder.go
index 70b006a8..44b94eaa 100644
--- a/manifest/schema2/builder.go
+++ b/manifest/schema2/builder.go
@@ -55,6 +55,9 @@ func (mb *builder) Build(ctx context.Context) (distribution.Manifest, error) {
 
 	// Add config to the blob store
 	m.Config, err = mb.bs.Put(ctx, MediaTypeConfig, mb.configJSON)
+	// Override MediaType, since Put always replaces the specified media
+	// type with application/octet-stream in the descriptor it returns.
+	m.Config.MediaType = MediaTypeConfig
 	if err != nil {
 		return nil, err
 	}
diff --git a/manifest/schema2/builder_test.go b/manifest/schema2/builder_test.go
index 6806033d..02ed401b 100644
--- a/manifest/schema2/builder_test.go
+++ b/manifest/schema2/builder_test.go
@@ -32,7 +32,7 @@ func (bs *mockBlobService) Put(ctx context.Context, mediaType string, p []byte)
 	d := distribution.Descriptor{
 		Digest:    digest.FromBytes(p),
 		Size:      int64(len(p)),
-		MediaType: mediaType,
+		MediaType: "application/octet-stream",
 	}
 	bs.descriptors[d.Digest] = d
 	return d, nil