diff --git a/test/sandbox.json b/test/sandbox.json
index 908c3b299..23a07709a 100644
--- a/test/sandbox.json
+++ b/test/sandbox.json
@@ -1,7 +1,7 @@
 {
     "genesis_pubkey":
        "edpkuSLWfVU1Vq7Jg9FucPyKmma6otcMHac9zG4oU1KMHSTBpJuGQ2",
-    "slot_durations" : [ 10 ; 5 ],
+    "slot_durations" : [ 10, 5 ],
     "cycle_length" : 128,
     "first_free_mining_slot" : 4
 }