diff --git a/bar.go b/bar.go
index 25a9e1b..c05ec42 100644
--- a/bar.go
+++ b/bar.go
@@ -42,7 +42,7 @@
 	recoveredPanic interface{}
 }
 
-type extFunc func(in io.Reader, reqWidth int, st decor.Statistics) (out io.Reader, lines int)
+type extenderFunc func(in io.Reader, reqWidth int, st decor.Statistics) (out io.Reader, lines int)
 
 type bState struct {
 	id                int
@@ -67,7 +67,7 @@
 	bufP, bufB, bufA  *bytes.Buffer
 	filler            BarFiller
 	middleware        func(BarFiller) BarFiller
-	extender          extFunc
+	extender          extenderFunc
 
 	// runningBar is a key for *pState.parkedBars
 	runningBar *Bar
@@ -475,7 +475,7 @@
 	}
 }
 
-func makePanicExtender(p interface{}) extFunc {
+func makePanicExtender(p interface{}) extenderFunc {
 	pstr := fmt.Sprint(p)
 	stack := debug.Stack()
 	stackLines := bytes.Count(stack, []byte("\n"))
diff --git a/bar_option.go b/bar_option.go
index d26c0b2..e359c11 100644
--- a/bar_option.go
+++ b/bar_option.go
@@ -111,11 +111,11 @@
 		return nil
 	}
 	return func(s *bState) {
-		s.extender = makeExtFunc(filler)
+		s.extender = makeExtenderFunc(filler)
 	}
 }
 
-func makeExtFunc(filler BarFiller) extFunc {
+func makeExtenderFunc(filler BarFiller) extenderFunc {
 	buf := new(bytes.Buffer)
 	return func(r io.Reader, reqWidth int, st decor.Statistics) (io.Reader, int) {
 		filler.Fill(buf, reqWidth, st)