diff --git a/lib/adapters/http.js b/lib/adapters/http.js
index 108f0a3058..9d8120d3bd 100755
--- a/lib/adapters/http.js
+++ b/lib/adapters/http.js
@@ -60,11 +60,10 @@ module.exports = function httpAdapter(config) {
 
     // Set User-Agent (required by some servers)
     // See https://github.com/axios/axios/issues/69
-    if ('User-Agent' in headers || 'user-agent' in headers) {
+    if ('user-agent' in headerNames) {
       // User-Agent is specified; handle case where no UA header is desired
-      if (!headers['User-Agent'] && !headers['user-agent']) {
-        delete headers['User-Agent'];
-        delete headers['user-agent'];
+      if (!headers[headerNames['user-agent']]) {
+        delete headers[headerNames['user-agent']];
       }
       // Otherwise, use specified value
     } else {