diff --git a/bar_filler_nop.go b/bar_filler_nop.go
index 97b33af..a23c61b 100644
--- a/bar_filler_nop.go
+++ b/bar_filler_nop.go
@@ -6,17 +6,17 @@
 	"github.com/vbauerster/mpb/v8/decor"
 )
 
-// BarFillerBuilderFunc is function type adapter to convert compatible
+// barFillerBuilderFunc is function type adapter to convert compatible
 // function into BarFillerBuilder interface.
-type BarFillerBuilderFunc func() BarFiller
+type barFillerBuilderFunc func() BarFiller
 
-func (f BarFillerBuilderFunc) Build() BarFiller {
+func (f barFillerBuilderFunc) Build() BarFiller {
 	return f()
 }
 
 // NopStyle provides BarFillerBuilder which builds NOP BarFiller.
 func NopStyle() BarFillerBuilder {
-	return BarFillerBuilderFunc(func() BarFiller {
+	return barFillerBuilderFunc(func() BarFiller {
 		return BarFillerFunc(func(io.Writer, decor.Statistics) error {
 			return nil
 		})