diff --git a/bar.go b/bar.go
index d18c7f4..218988a 100644
--- a/bar.go
+++ b/bar.go
@@ -19,7 +19,6 @@
 type Bar struct {
 	index          int // used by heap
 	priority       int // used by heap
-	hasEwma        bool
 	frameCh        chan *renderFrame
 	operateState   chan func(*bState)
 	done           chan struct{}
@@ -73,7 +72,6 @@
 
 	bar := &Bar{
 		priority:     bs.priority,
-		hasEwma:      len(bs.ewmaDecorators) != 0,
 		frameCh:      make(chan *renderFrame, 1),
 		operateState: make(chan func(*bState)),
 		done:         make(chan struct{}),
@@ -94,11 +92,12 @@
 	if r == nil {
 		panic("expected non nil io.Reader")
 	}
-	select {
+	result := make(chan bool)
+	select {
+	case b.operateState <- func(s *bState) { result <- len(s.ewmaDecorators) != 0 }:
+		return b.newProxyReader(r, <-result)
 	case <-b.done:
 		return nil
-	default:
-		return b.newProxyReader(r)
 	}
 }
 
diff --git a/proxyreader.go b/proxyreader.go
index 51b63ea..193ef0a 100644
--- a/proxyreader.go
+++ b/proxyreader.go
@@ -54,16 +54,16 @@
 	return n, err
 }
 
-func (b *Bar) newProxyReader(r io.Reader) (rc io.ReadCloser) {
+func (b *Bar) newProxyReader(r io.Reader, hasEwma bool) (rc io.ReadCloser) {
 	pr := proxyReader{toReadCloser(r), b}
 	if wt, ok := r.(io.WriterTo); ok {
 		pw := proxyWriterTo{pr, wt}
-		if b.hasEwma {
+		if hasEwma {
 			rc = ewmaProxyWriterTo{ewmaProxyReader{pr}, pw}
 		} else {
 			rc = pw
 		}
-	} else if b.hasEwma {
+	} else if hasEwma {
 		rc = ewmaProxyReader{pr}
 	} else {
 		rc = pr