diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index c192ed6a1c..43b26092e3 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -25,7 +25,12 @@ transform._ensureTransformerNames = function (type, keys) {
   for (var i = 0; i < keys.length; i++) {
     var key = keys[i];
     if (!_.has(transform.transformers, key)) {
-      throw new ReferenceError("unknown transformer " + key + " specified in " + type);
+      throw new ReferenceError(
+        "Unknown transformer " + key + " specified in " + type + " - " +
+        "transformer key names have been changed in 3.0.0 see " +
+        "the changelog for more info " +
+        "https://github.com/6to5/6to5/blob/master/CHANGELOG.md#300"
+      );
     }
   }
 };
diff --git a/test/fixtures/transformation/api/unknown-transformer-in-list/options.json b/test/fixtures/transformation/api/unknown-transformer-in-list/options.json
index 4d99240340..760c2f32c7 100644
--- a/test/fixtures/transformation/api/unknown-transformer-in-list/options.json
+++ b/test/fixtures/transformation/api/unknown-transformer-in-list/options.json
@@ -1,4 +1,4 @@
 {
-  "throws": "unknown transformer arrowFunctions2 specified in whitelist",
+  "throws": "Unknown transformer arrowFunctions2 specified in whitelist",
   "whitelist": ["arrowFunctions2"]
 }