diff --git a/stream.go b/stream.go
index e396b1fa..21c51e8f 100644
--- a/stream.go
+++ b/stream.go
@@ -154,7 +154,7 @@ type clientStream struct {
 
 	tracing bool // set to EnableTracing when the clientStream is created.
 
-	mu sync.Mutex // protects trInfo
+	mu sync.Mutex // protects trInfo.tr
 	// trInfo.tr is set when the clientStream is created (if EnableTracing is true),
 	// and is set to nil when the clientStream's finish method is called.
 	trInfo traceInfo