diff --git a/bar_filler.go b/bar_filler.go
index 5ac343c..379cfea 100644
--- a/bar_filler.go
+++ b/bar_filler.go
@@ -29,11 +29,3 @@
 func (f BarFillerFunc) Fill(w io.Writer, stat decor.Statistics) error {
 	return f(w, stat)
 }
-
-// BarFillerBuilderFunc is function type adapter to convert compatible
-// function into BarFillerBuilder interface.
-type BarFillerBuilderFunc func() BarFiller
-
-func (f BarFillerBuilderFunc) Build() BarFiller {
-	return f()
-}
diff --git a/bar_filler_nop.go b/bar_filler_nop.go
index f7947f1..97b33af 100644
--- a/bar_filler_nop.go
+++ b/bar_filler_nop.go
@@ -5,6 +5,14 @@
 
 	"github.com/vbauerster/mpb/v8/decor"
 )
+
+// BarFillerBuilderFunc is function type adapter to convert compatible
+// function into BarFillerBuilder interface.
+type BarFillerBuilderFunc func() BarFiller
+
+func (f BarFillerBuilderFunc) Build() BarFiller {
+	return f()
+}
 
 // NopStyle provides BarFillerBuilder which builds NOP BarFiller.
 func NopStyle() BarFillerBuilder {