diff --git a/json_test.go b/json_test.go
index a61c4e0..1be6c15 100644
--- a/json_test.go
+++ b/json_test.go
@@ -223,6 +223,9 @@ func trim(b []byte) []byte {
 var jsonBig []byte
 
 func initBig() {
+	if len(jsonBig) > 0 {
+		return
+	}
 	n := 10000
 	if testing.Short() {
 		n = 100