diff --git a/.travis.yml b/.travis.yml
index 4312dc6d..e29bd240 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,7 +19,7 @@ before_install:
   - nvm use $TRAVIS_NODE_VERSION
   - npm set loglevel error
   - npm set progress false
-  - 'if [ $PKG_CMD = "yarn" ]; then npm i -g yarn@0.18.2 ; fi'
+  - 'if [ $PKG_CMD = "yarn" ]; then npm i -g yarn@0.22.0 ; fi'
 install:
   - $PKG_CMD install
 script:
diff --git a/data/plugin-features.js b/data/plugin-features.js
index bd87fd41..82d0e9df 100644
--- a/data/plugin-features.js
+++ b/data/plugin-features.js
@@ -39,6 +39,11 @@ module.exports = {
       "destructuring, parameters",
     ],
   },
+  "transform-es2015-duplicate-keys": {
+    features: [
+      "miscellaneous / duplicate property names in strict mode",
+    ],
+  },
   "transform-es2015-for-of": {
     features: [
       "for..of loops",
diff --git a/data/plugins.json b/data/plugins.json
index 6630092e..bf3a8778 100644
--- a/data/plugins.json
+++ b/data/plugins.json
@@ -34,6 +34,15 @@
     "ios": 10,
     "opera": 33
   },
+  "transform-es2015-duplicate-keys": {
+    "chrome": 42,
+    "edge": 12,
+    "firefox": 34,
+    "safari": 9,
+    "node": 4,
+    "ios": 9,
+    "opera": 29
+  },
   "transform-es2015-computed-properties": {
     "chrome": 44,
     "edge": 12,
diff --git a/test/debug-fixtures/builtins-uglify/stdout.txt b/test/debug-fixtures/builtins-uglify/stdout.txt
index 0cfe3cc4..1ce53032 100644
--- a/test/debug-fixtures/builtins-uglify/stdout.txt
+++ b/test/debug-fixtures/builtins-uglify/stdout.txt
@@ -13,6 +13,7 @@ Using plugins:
   transform-es2015-block-scoped-functions {"uglify":true}
   transform-es2015-block-scoping {"uglify":true}
   transform-es2015-classes {"uglify":true}
+  transform-es2015-duplicate-keys {"uglify":true}
   transform-es2015-computed-properties {"uglify":true}
   check-es2015-constants {"uglify":true}
   transform-es2015-destructuring {"uglify":true}
diff --git a/test/debug-fixtures/builtins/stdout.txt b/test/debug-fixtures/builtins/stdout.txt
index c25134be..11042836 100644
--- a/test/debug-fixtures/builtins/stdout.txt
+++ b/test/debug-fixtures/builtins/stdout.txt
@@ -14,6 +14,7 @@ Using plugins:
   transform-es2015-block-scoped-functions {"ie":10}
   transform-es2015-block-scoping {"ie":10}
   transform-es2015-classes {"ie":10}
+  transform-es2015-duplicate-keys {"ie":10}
   transform-es2015-computed-properties {"ie":10}
   check-es2015-constants {"ie":10}
   transform-es2015-destructuring {"ie":10,"node":6}
@@ -110,4 +111,4 @@ Using polyfills:
   web.timers {"chrome":54,"ie":10,"node":6}
   web.immediate {"chrome":54,"ie":10,"node":6}
   web.dom.iterable {"chrome":54,"ie":10,"node":6}
-src/in.js -> lib/in.js
+src/in.js -> lib/in.js
\ No newline at end of file
diff --git a/test/debug-fixtures/plugins-only/stdout.txt b/test/debug-fixtures/plugins-only/stdout.txt
index 5263ed55..a2ccd28b 100644
--- a/test/debug-fixtures/plugins-only/stdout.txt
+++ b/test/debug-fixtures/plugins-only/stdout.txt
@@ -14,4 +14,4 @@ Using plugins:
   transform-es2015-function-name {"firefox":52}
   transform-es2015-literals {"firefox":52}
   syntax-trailing-function-commas {"node":7.4}
-src/in.js -> lib/in.js
+src/in.js -> lib/in.js
\ No newline at end of file
diff --git a/test/debug-fixtures/specific-targets/stdout.txt b/test/debug-fixtures/specific-targets/stdout.txt
index 3300cba2..9372c273 100644
--- a/test/debug-fixtures/specific-targets/stdout.txt
+++ b/test/debug-fixtures/specific-targets/stdout.txt
@@ -17,6 +17,7 @@ Using plugins:
   transform-es2015-block-scoped-functions {"edge":13,"ie":10,"ios":9,"safari":7}
   transform-es2015-block-scoping {"edge":13,"firefox":49,"ie":10,"ios":9,"safari":7}
   transform-es2015-classes {"ie":10,"ios":9,"safari":7}
+  transform-es2015-duplicate-keys {"ie":10,"safari":7}
   transform-es2015-computed-properties {"ie":10,"safari":7}
   check-es2015-constants {"edge":13,"firefox":49,"ie":10,"ios":9,"safari":7}
   transform-es2015-destructuring {"edge":13,"firefox":49,"ie":10,"ios":9,"safari":7}
diff --git a/test/fixtures/preset-options/transform-duplicate-keys/actual.js b/test/fixtures/preset-options/transform-duplicate-keys/actual.js
new file mode 100644
index 00000000..d7bc7a47
--- /dev/null
+++ b/test/fixtures/preset-options/transform-duplicate-keys/actual.js
@@ -0,0 +1 @@
+var a = { b:1, b: 2};
diff --git a/test/fixtures/preset-options/transform-duplicate-keys/expected.js b/test/fixtures/preset-options/transform-duplicate-keys/expected.js
new file mode 100644
index 00000000..5f926665
--- /dev/null
+++ b/test/fixtures/preset-options/transform-duplicate-keys/expected.js
@@ -0,0 +1,3 @@
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+
+var a = _defineProperty({ b: 1 }, "b", 2);
\ No newline at end of file
diff --git a/test/fixtures/preset-options/transform-duplicate-keys/options.json b/test/fixtures/preset-options/transform-duplicate-keys/options.json
new file mode 100644
index 00000000..1f29c71c
--- /dev/null
+++ b/test/fixtures/preset-options/transform-duplicate-keys/options.json
@@ -0,0 +1,7 @@
+{
+  "presets": [
+    ["../../../../lib", {
+      "modules": false
+    }]
+  ]
+}