diff --git a/exercises/hamming/canonical-data.json b/exercises/hamming/canonical-data.json
index 373ac58324..90fcd0a07a 100644
--- a/exercises/hamming/canonical-data.json
+++ b/exercises/hamming/canonical-data.json
@@ -1,6 +1,6 @@
 {
 "exercise": "hamming",
-"version": "1.1.0",
+"version": "2.0.0",
   "comments": [
     "Language implementations vary on the issue of unequal length strands.",
     "A language may elect to simplify this task by only presenting equal",
@@ -110,14 +110,14 @@
       "property": "distance",
       "strand1": "AATG",
       "strand2": "AAA",
-      "expected": -1
+      "expected": {"error": "left and right strands must be of equal length"}
     },
     {
       "description": "disallow second strand longer",
       "property": "distance",
       "strand1": "ATA",
       "strand2": "AGTG",
-      "expected": -1
+      "expected": {"error": "left and right strands must be of equal length"}
     }
   ]
 }