diff --git a/vng/object.go b/vng/object.go
index 9ea7a52b10..95e84989ad 100644
--- a/vng/object.go
+++ b/vng/object.go
@@ -175,7 +175,7 @@ func (o *Object) newSectionReader(level int, sectionOff int64) *zngio.Reader {
 	off += sectionOff
 	len -= sectionOff
 	reader := io.NewSectionReader(o.readerAt, off, len)
-	return zngio.NewReader(o.zctx, reader)
+	return zngio.NewReaderWithOpts(o.zctx, reader, zngio.ReaderOpts{Threads: 1})
 }
 
 func (o *Object) NewReassemblyReader() *zngio.Reader {
diff --git a/zio/zngio/trailer.go b/zio/zngio/trailer.go
index e138816af0..6fa46a55fe 100644
--- a/zio/zngio/trailer.go
+++ b/zio/zngio/trailer.go
@@ -126,7 +126,7 @@ func findCandidate(b []byte, off int) int {
 	}
 }
 func readTrailer(b []byte) *zed.Value {
-	val, _ := NewReader(zed.NewContext(), bytes.NewReader(b)).Read()
+	val, _ := NewReaderWithOpts(zed.NewContext(), bytes.NewReader(b), ReaderOpts{Threads: 1}).Read()
 	return val
 }