diff --git a/bar.go b/bar.go
index eda7f20..8b9e856 100644
--- a/bar.go
+++ b/bar.go
@@ -29,12 +29,12 @@
 	f(w, width, stat)
 }
 
-// BaseFiller interface.
-// If you ever need to implement a custom Filler based on mpb.NewBarFiller,
-// then you may need to implement this one as well, in order to retain
-// functionality of some `BarOption`s and method like *Bar.SetRefill.
-type BaseFiller interface {
-	BaseFiller() Filler
+// Wrapper interface.
+// If you're implementing custom Filler by wrapping a built-in one,
+// it is necessary to implement this interface to retain functionality
+// of built-in Filler.
+type Wrapper interface {
+	Base() Filler
 }
 
 // Bar represents a progress Bar.
diff --git a/progress.go b/progress.go
index 4a0f3c1..546d7a1 100644
--- a/progress.go
+++ b/progress.go
@@ -332,7 +332,7 @@
 func (s *pState) makeBarState(total int64, filler Filler, options ...BarOption) *bState {
 	bs := &bState{
 		total:    total,
-		baseF:    filler,
+		baseF:    extractBaseFiller(filler),
 		filler:   filler,
 		priority: s.idCount,
 		id:       s.idCount,
@@ -341,10 +341,6 @@
 		extender: func(r io.Reader, _ int, _ *decor.Statistics) (io.Reader, int) {
 			return r, 0
 		},
-	}
-
-	if f, ok := filler.(BaseFiller); ok {
-		bs.baseF = f.BaseFiller()
 	}
 
 	for _, opt := range options {
@@ -412,3 +408,10 @@
 
 	return multiplexedStream
 }
+
+func extractBaseFiller(f Filler) Filler {
+	if f, ok := f.(Wrapper); ok {
+		return extractBaseFiller(f.Base())
+	}
+	return f
+}