diff --git a/lib/core/mergeConfig.js b/lib/core/mergeConfig.js
index 827d6df..5d9b042 100644
--- a/lib/core/mergeConfig.js
+++ b/lib/core/mergeConfig.js
@@ -22,7 +22,7 @@ module.exports = function mergeConfig(config1, config2) {
     'timeout', 'withCredentials', 'adapter', 'responseType', 'xsrfCookieName',
     'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress',
     'maxContentLength', 'validateStatus', 'maxRedirects', 'httpAgent',
-    'httpsAgent', 'cancelToken', 'socketPath'
+    'httpsAgent', 'cancelToken', 'socketPath', 'responseEncoding'
   ];
 
   utils.forEach(valueFromConfig2Keys, function valueFromConfig2(prop) {