diff --git a/bar_filler.go b/bar_filler.go
index 2d672da..af845da 100644
--- a/bar_filler.go
+++ b/bar_filler.go
@@ -9,7 +9,7 @@
 // BarFiller interface.
 // Bar (without decorators) renders itself by calling BarFiller's Fill method.
 type BarFiller interface {
-	Fill(w io.Writer, stat decor.Statistics)
+	Fill(w io.Writer, stat decor.Statistics) error
 }
 
 // BarFillerBuilder interface.
@@ -24,10 +24,10 @@
 
 // BarFillerFunc is function type adapter to convert compatible function
 // into BarFiller interface.
-type BarFillerFunc func(w io.Writer, stat decor.Statistics)
+type BarFillerFunc func(w io.Writer, stat decor.Statistics) error
 
-func (f BarFillerFunc) Fill(w io.Writer, stat decor.Statistics) {
-	f(w, stat)
+func (f BarFillerFunc) Fill(w io.Writer, stat decor.Statistics) error {
+	return f(w, stat)
 }
 
 // BarFillerBuilderFunc is function type adapter to convert compatible