diff --git a/bar.go b/bar.go
index b912208..9ae1121 100644
--- a/bar.go
+++ b/bar.go
@@ -457,7 +457,10 @@
 	for _, d := range s.pDecorators {
 		str := d.Decor(stat)
 		stat.AvailableWidth -= runewidth.StringWidth(stripansi.Strip(str))
-		bufP.WriteString(str)
+		_, err := bufP.WriteString(str)
+		if err != nil {
+			panic(err)
+		}
 	}
 	if stat.AvailableWidth < 1 {
 		trunc := strings.NewReader(runewidth.Truncate(stripansi.Strip(bufP.String()), tw, "…"))
@@ -475,7 +478,10 @@
 	for _, d := range s.aDecorators {
 		str := d.Decor(stat)
 		stat.AvailableWidth -= runewidth.StringWidth(stripansi.Strip(str))
-		bufA.WriteString(str)
+		_, err := bufA.WriteString(str)
+		if err != nil {
+			panic(err)
+		}
 	}
 	if stat.AvailableWidth < 1 {
 		trunc := strings.NewReader(runewidth.Truncate(stripansi.Strip(bufA.String()), tw, "…"))
@@ -483,7 +489,10 @@
 		return io.MultiReader(bufP, bufB, trunc, nlr)
 	}
 
-	s.filler.Fill(bufB, stat)
+	err := s.filler.Fill(bufB, stat)
+	if err != nil {
+		panic(err)
+	}
 
 	return io.MultiReader(bufP, bufB, bufA, nlr)
 }
diff --git a/bar_option.go b/bar_option.go
index 2a6b637..bf3d5d5 100644
--- a/bar_option.go
+++ b/bar_option.go
@@ -88,15 +88,12 @@
 // BarFillerOnComplete replaces bar's filler with message, on complete event.
 func BarFillerOnComplete(message string) BarOption {
 	return BarFillerMiddleware(func(base BarFiller) BarFiller {
-		return BarFillerFunc(func(w io.Writer, st decor.Statistics) {
+		return BarFillerFunc(func(w io.Writer, st decor.Statistics) error {
 			if st.Completed {
 				_, err := io.WriteString(w, message)
-				if err != nil {
-					panic(err)
-				}
-			} else {
-				base.Fill(w, st)
+				return err
 			}
+			return base.Fill(w, st)
 		})
 	})
 }