diff --git a/decor/decorators.go b/decor/decorators.go
index cae1783..3147aa1 100644
--- a/decor/decorators.go
+++ b/decor/decorators.go
@@ -239,6 +239,9 @@
 	}
 }
 
+// EwmaETA is a struct, which implements ewma based ETA decorator.
+// Should not be used directly, use ETA(int, float64, chan time.Time, ...WC)
+// func helper instead.
 type EwmaETA struct {
 	ewma.MovingAverage
 	StartBlockCh chan time.Time