diff --git a/src/main/scala/gitbucket/core/controller/IndexController.scala b/src/main/scala/gitbucket/core/controller/IndexController.scala
index ba3cfd8..6bc2751 100644
--- a/src/main/scala/gitbucket/core/controller/IndexController.scala
+++ b/src/main/scala/gitbucket/core/controller/IndexController.scala
@@ -117,7 +117,9 @@
    * JSON API for checking user existence.
    */
   post("/_user/existence")(usersOnly {
-    getAccountByUserName(params("userName")).isDefined
+    getAccountByUserName(params("userName")).map { account =>
+      if(params.get("userOnly").isDefined) !account.isGroupAccount else true
+    } getOrElse false
   })
 
   // TODO Move to RepositoryViwerController?
diff --git a/src/main/twirl/gitbucket/core/admin/usergroup.scala.html b/src/main/twirl/gitbucket/core/admin/usergroup.scala.html
index b9f6171..ac8044d 100644
--- a/src/main/twirl/gitbucket/core/admin/usergroup.scala.html
+++ b/src/main/twirl/gitbucket/core/admin/usergroup.scala.html
@@ -78,7 +78,8 @@
 
     // check existence
     $.post('@path/_user/existence', {
-      'userName': userName
+      'userName': userName,
+      'userOnly': true
     }, function(data, status){
       if(data == 'true'){
         addMemberHTML(userName, false);