diff --git a/.6to5rc b/.6to5rc
new file mode 100644
index 0000000000..82024762c5
--- /dev/null
+++ b/.6to5rc
@@ -0,0 +1,5 @@
+{
+  "experimental": true,
+  "playground": true,
+  "loose": true
+}
diff --git a/Makefile b/Makefile
index 7ce426fcb9..71fe9fd1e2 100644
--- a/Makefile
+++ b/Makefile
@@ -5,10 +5,17 @@ UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs
 JSHINT_CMD = node_modules/jshint/bin/jshint
 MOCHA_CMD = node_modules/mocha/bin/_mocha
 JSCS_CMD = node_modules/jscs/bin/jscs
+6TO5_CMD = node_modules/6to5/bin/6to5
 
 export NODE_ENV = test
 
-.PHONY: clean test test-cov test-clean lint test-travis test-simple test-all test-browser publish build bootstrap publish-core publish-runtime
+.PHONY: clean test test-cov test-clean lint test-travis test-simple test-all test-browser publish build bootstrap publish-core publish-runtime build-core watch-core
+
+build-core:
+	#node $(6TO5_CMD) src --out-dir lib
+
+watch-core:
+	#node $(6TO5_CMD) src --out-dir lib --watch
 
 build:
 	mkdir -p dist
@@ -55,7 +62,7 @@ test-cov:
 	export SIMPLE_6TO5_TESTS=1; \
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) --
 
-test-travis: bootstrap
+test-travis: build-core bootstrap
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) --
 	if test -n "$$CODECLIMATE_REPO_TOKEN"; then codeclimate < coverage/lcov.info; fi
 
diff --git a/appveyor.yml b/appveyor.yml
deleted file mode 100644
index 859718768c..0000000000
--- a/appveyor.yml
+++ /dev/null
@@ -1,17 +0,0 @@
-environment:
-  matrix:
-    - nodejs_version: "0.10"
-    - nodejs_version: "0.11"
-
-install:
- - "npm install"
- - "cinst make"
-
-test_script:
- - "node --version"
- - "npm --version"
- - "make test-spec"
-
-build: "off"
-
-version: "{build}"
diff --git a/lib/6to5/transformation/templates/.6to5rc b/lib/6to5/transformation/templates/.6to5rc
new file mode 100644
index 0000000000..a5a58b5836
--- /dev/null
+++ b/lib/6to5/transformation/templates/.6to5rc
@@ -0,0 +1,3 @@
+{
+  "blacklist": ["useStrict"]
+}
diff --git a/package.json b/package.json
index 5f24b5f4e4..8ade80997a 100644
--- a/package.json
+++ b/package.json
@@ -58,6 +58,7 @@
     "useragent": "^2.1.5"
   },
   "devDependencies": {
+    "6to5": "3.5.3",
     "browserify": "8.1.1",
     "chai": "1.10.0",
     "esvalid": "1.1.0",