diff --git a/bar.go b/bar.go
index 8cbd625..41a8d7a 100644
--- a/bar.go
+++ b/bar.go
@@ -34,7 +34,7 @@
 }
 
 type Filler interface {
-	fill(w io.Writer, width int, s *decor.Statistics)
+	Fill(w io.Writer, width int, s *decor.Statistics)
 }
 
 type (
@@ -349,9 +349,9 @@
 	}
 
 	if prependCount+s.width+appendCount > termWidth {
-		s.filler.fill(s.bufB, termWidth-prependCount-appendCount, stat)
+		s.filler.Fill(s.bufB, termWidth-prependCount-appendCount, stat)
 	} else {
-		s.filler.fill(s.bufB, s.width, stat)
+		s.filler.Fill(s.bufB, s.width, stat)
 	}
 
 	if !s.trimSpace {
diff --git a/bar_filler.go b/bar_filler.go
index 232c23a..f58e187 100644
--- a/bar_filler.go
+++ b/bar_filler.go
@@ -23,7 +23,7 @@
 	refill *refill
 }
 
-func (s *barFiller) fill(w io.Writer, width int, stat *decor.Statistics) {
+func (s *barFiller) Fill(w io.Writer, width int, stat *decor.Statistics) {
 
 	str := string(s.format[rLeft])
 
diff --git a/spinner_filler.go b/spinner_filler.go
index 2ba70c4..c44e3eb 100644
--- a/spinner_filler.go
+++ b/spinner_filler.go
@@ -23,7 +23,7 @@
 	alignment SpinnerAlignment
 }
 
-func (s *spinnerFiller) fill(w io.Writer, width int, stat *decor.Statistics) {
+func (s *spinnerFiller) Fill(w io.Writer, width int, stat *decor.Statistics) {
 
 	frame := s.frames[stat.Current%int64(len(s.frames))]
 	frameWidth := utf8.RuneCountInString(frame)