diff --git a/decor/size_type.go b/decor/size_type.go
index 232788e..ebddce9 100644
--- a/decor/size_type.go
+++ b/decor/size_type.go
@@ -10,7 +10,9 @@
 
 var (
 	_ fmt.Formatter = SizeB1024(0)
+	_ fmt.Stringer  = SizeB1024(0)
 	_ fmt.Formatter = SizeB1000(0)
+	_ fmt.Stringer  = SizeB1000(0)
 )
 
 const (