diff --git a/bar_filler_bar.go b/bar_filler_bar.go
index 54b7bfd..d8bf90a 100644
--- a/bar_filler_bar.go
+++ b/bar_filler_bar.go
@@ -157,9 +157,8 @@
 		return
 	}
 
-	ow := optimisticWriter(w)
-	ow(s.components[iLbound].bytes)
-	defer ow(s.components[iRbound].bytes)
+	mustWrite(w, s.components[iLbound].bytes)
+	defer mustWrite(w, s.components[iRbound].bytes)
 
 	if width == 0 {
 		return
@@ -231,26 +230,24 @@
 	}
 
 	if s.rev {
-		flush(ow, padding, filling)
+		flush(w, padding, filling)
 	} else {
-		flush(ow, filling, padding)
-	}
-}
-
-func flush(ow func([]byte), filling, padding [][]byte) {
+		flush(w, filling, padding)
+	}
+}
+
+func flush(w io.Writer, filling, padding [][]byte) {
 	for i := len(filling) - 1; i >= 0; i-- {
-		ow(filling[i])
+		mustWrite(w, filling[i])
 	}
 	for i := 0; i < len(padding); i++ {
-		ow(padding[i])
-	}
-}
-
-func optimisticWriter(w io.Writer) func([]byte) {
-	return func(p []byte) {
-		_, err := w.Write(p)
-		if err != nil {
-			panic(err)
-		}
-	}
-}
+		mustWrite(w, padding[i])
+	}
+}
+
+func mustWrite(w io.Writer, p []byte) {
+	_, err := w.Write(p)
+	if err != nil {
+		panic(err)
+	}
+}
diff --git a/decor/optimistic_string_writer.go b/decor/optimistic_string_writer.go
index ea9fda7..c6a3438 100644
--- a/decor/optimistic_string_writer.go
+++ b/decor/optimistic_string_writer.go
@@ -2,11 +2,9 @@
 
 import "io"
 
-func optimisticStringWriter(w io.Writer) func(string) {
-	return func(s string) {
-		_, err := io.WriteString(w, s)
-		if err != nil {
-			panic(err)
-		}
+func mustWriteString(w io.Writer, s string) {
+	_, err := io.WriteString(w, s)
+	if err != nil {
+		panic(err)
 	}
 }
diff --git a/decor/percentage.go b/decor/percentage.go
index 6e7f5c6..e726689 100644
--- a/decor/percentage.go
+++ b/decor/percentage.go
@@ -23,12 +23,11 @@
 		}
 	}
 
-	osw := optimisticStringWriter(st)
-	osw(strconv.FormatFloat(float64(s), 'f', prec, 64))
+	mustWriteString(st, strconv.FormatFloat(float64(s), 'f', prec, 64))
 	if st.Flag(' ') {
-		osw(" ")
+		mustWriteString(st, " ")
 	}
-	osw("%")
+	mustWriteString(st, "%")
 }
 
 // Percentage returns percentage decorator. It's a wrapper of NewPercentage.
diff --git a/decor/size_type.go b/decor/size_type.go
index 12879b8..09ecc23 100644
--- a/decor/size_type.go
+++ b/decor/size_type.go
@@ -49,12 +49,11 @@
 		unit = _iTiB
 	}
 
-	osw := optimisticStringWriter(st)
-	osw(strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
+	mustWriteString(st, strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
 	if st.Flag(' ') {
-		osw(" ")
+		mustWriteString(st, " ")
 	}
-	osw(unit.String())
+	mustWriteString(st, unit.String())
 }
 
 const (
@@ -98,10 +97,9 @@
 		unit = _TB
 	}
 
-	osw := optimisticStringWriter(st)
-	osw(strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
+	mustWriteString(st, strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
 	if st.Flag(' ') {
-		osw(" ")
+		mustWriteString(st, " ")
 	}
-	osw(unit.String())
+	mustWriteString(st, unit.String())
 }
diff --git a/decor/speed.go b/decor/speed.go
index 99cfde2..f052352 100644
--- a/decor/speed.go
+++ b/decor/speed.go
@@ -23,7 +23,7 @@
 
 func (self *speedFormatter) Format(st fmt.State, verb rune) {
 	self.Formatter.Format(st, verb)
-	optimisticStringWriter(st)("/s")
+	mustWriteString(st, "/s")
 }
 
 // EwmaSpeed exponential-weighted-moving-average based speed decorator.