diff --git a/bar.go b/bar.go
index 239a583..5f6e1f7 100644
--- a/bar.go
+++ b/bar.go
@@ -91,10 +91,12 @@
 	if r == nil {
 		panic("expected non nil io.Reader")
 	}
-	result := make(chan bool)
-	select {
-	case b.operateState <- func(s *bState) { result <- len(s.ewmaDecorators) != 0 }:
-		return newProxyReader(r, b, <-result)
+	result := make(chan io.ReadCloser)
+	select {
+	case b.operateState <- func(s *bState) {
+		result <- newProxyReader(r, b, len(s.ewmaDecorators) != 0)
+	}:
+		return <-result
 	case <-b.ctx.Done():
 		return nil
 	}
@@ -107,10 +109,12 @@
 	if w == nil {
 		panic("expected non nil io.Writer")
 	}
-	result := make(chan bool)
-	select {
-	case b.operateState <- func(s *bState) { result <- len(s.ewmaDecorators) != 0 }:
-		return newProxyWriter(w, b, <-result)
+	result := make(chan io.WriteCloser)
+	select {
+	case b.operateState <- func(s *bState) {
+		result <- newProxyWriter(w, b, len(s.ewmaDecorators) != 0)
+	}:
+		return <-result
 	case <-b.ctx.Done():
 		return nil
 	}