diff --git a/modules/swagger-codegen/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache b/modules/swagger-codegen/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache
index 567fc6d25db..54f2b14573b 100644
--- a/modules/swagger-codegen/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache
+++ b/modules/swagger-codegen/src/main/resources/Java/libraries/resttemplate/ApiClient.mustache
@@ -268,6 +268,9 @@ public class ApiClient {
      * @return ApiClient this client
      */
     public ApiClient addDefaultHeader(String name, String value) {
+        if (defaultHeaders.containsKey(name)) {
+            defaultHeaders.remove(name);
+        }
         defaultHeaders.add(name, value);
         return this;
     }