diff --git a/tests/unit/graphs/example.json b/tests/unit/graphs/example.json
index b256553..a891f90 100644
--- a/tests/unit/graphs/example.json
+++ b/tests/unit/graphs/example.json
@@ -74,6 +74,7 @@
                   "x":560,
                   "y":130
                },
+               "key":true,
                "cell":[
                   "15",
                   "16"