diff --git a/test/fixtures/eckey.json b/test/fixtures/eckey.json
index 923ed42..fff0164 100644
--- a/test/fixtures/eckey.json
+++ b/test/fixtures/eckey.json
@@ -67,6 +67,10 @@
   ],
   "invalid": {
     "constructor": [
+      {
+        "exception": "Private key must be greater than 0",
+        "D": "-1"
+      },
       {
         "exception": "Private key must be greater than 0",
         "D": "0"