diff --git a/bar.go b/bar.go
index 0301b18..c708077 100644
--- a/bar.go
+++ b/bar.go
@@ -27,7 +27,7 @@
 }
 
 type syncTable [2][]chan int
-type extenderFunc func([]io.Reader, decor.Statistics) ([]io.Reader, error)
+type extenderFunc func(decor.Statistics, ...io.Reader) ([]io.Reader, error)
 
 // bState is actual bar's state.
 type bState struct {
@@ -427,10 +427,7 @@
 			b.frameCh <- frame
 			return
 		}
-		frame.rows = append(frame.rows, r)
-		if s.extender != nil {
-			frame.rows, frame.err = s.extender(frame.rows, stat)
-		}
+		frame.rows, frame.err = s.extender(stat, r)
 		if s.aborted || s.completed() {
 			frame.shutdown = s.shutdown
 			frame.rmOnComplete = s.rmOnComplete
diff --git a/bar_option.go b/bar_option.go
index d001db3..64d2e18 100644
--- a/bar_option.go
+++ b/bar_option.go
@@ -122,28 +122,27 @@
 
 func makeExtenderFunc(filler BarFiller, rev bool) extenderFunc {
 	buf := new(bytes.Buffer)
-	base := func(rows []io.Reader, stat decor.Statistics) ([]io.Reader, error) {
+	base := func(stat decor.Statistics, rows ...io.Reader) ([]io.Reader, error) {
 		err := filler.Fill(buf, stat)
 		if err != nil {
 			buf.Reset()
 			return rows, err
 		}
 		for {
-			b, err := buf.ReadBytes('\n')
+			line, err := buf.ReadBytes('\n')
 			if err != nil {
 				buf.Reset()
 				break
 			}
-			rows = append(rows, bytes.NewReader(b))
+			rows = append(rows, bytes.NewReader(line))
 		}
 		return rows, err
 	}
-
 	if !rev {
 		return base
 	}
-	return func(rows []io.Reader, stat decor.Statistics) ([]io.Reader, error) {
-		rows, err := base(rows, stat)
+	return func(stat decor.Statistics, rows ...io.Reader) ([]io.Reader, error) {
+		rows, err := base(stat, rows...)
 		if err != nil {
 			return rows, err
 		}
diff --git a/progress.go b/progress.go
index 8009faf..09abd29 100644
--- a/progress.go
+++ b/progress.go
@@ -11,6 +11,7 @@
 	"time"
 
 	"github.com/vbauerster/mpb/v8/cwriter"
+	"github.com/vbauerster/mpb/v8/decor"
 )
 
 const defaultRefreshRate = 150 * time.Millisecond
@@ -435,6 +436,9 @@
 		filler:      filler,
 		renderReq:   s.renderReq,
 		autoRefresh: s.autoRefresh,
+		extender: func(_ decor.Statistics, rows ...io.Reader) ([]io.Reader, error) {
+			return rows, nil
+		},
 	}
 
 	if total > 0 {