diff --git a/src/main/scala/gitbucket/core/controller/IndexController.scala b/src/main/scala/gitbucket/core/controller/IndexController.scala
index 8d15b2e..51d26f6 100644
--- a/src/main/scala/gitbucket/core/controller/IndexController.scala
+++ b/src/main/scala/gitbucket/core/controller/IndexController.scala
@@ -118,12 +118,13 @@
   })
 
   /**
-   * JSON API for checking user existence.
+   * JSON API for checking user or group existence.
+   * Returns a single string which is any of "group", "user" or "".
    */
   post("/_user/existence")(usersOnly {
     getAccountByUserName(params("userName")).map { account =>
-      if(params.get("userOnly").isDefined) !account.isGroupAccount else true
-    } getOrElse false
+      if(account.isGroupAccount) "group" else "user"
+    } getOrElse ""
   })
 
   // TODO Move to RepositoryViwerController?
diff --git a/src/main/twirl/gitbucket/core/account/group.scala.html b/src/main/twirl/gitbucket/core/account/group.scala.html
index 1bda182..cb219da 100644
--- a/src/main/twirl/gitbucket/core/account/group.scala.html
+++ b/src/main/twirl/gitbucket/core/account/group.scala.html
@@ -80,15 +80,14 @@
     }
 
     // check existence
-    $.post('@context.path/_user/existence', {
-      'userName': userName
-    }, function(data, status){
-      if(data == 'true'){
-        addMemberHTML(userName, false);
-      } else {
-        $('#error-members').text('User does not exist.');
-      }
-    });
+    $.post('@context.path/_user/existence', { 'userName': userName },
+      function(data, status){
+        if(data == 'user'){
+          addMemberHTML(userName, false);
+        } else {
+          $('#error-members').text('User does not exist.');
+        }
+      });
   });
 
   $(document).on('click', '.remove', function(){
diff --git a/src/main/twirl/gitbucket/core/admin/usergroup.scala.html b/src/main/twirl/gitbucket/core/admin/usergroup.scala.html
index ec99a73..1677005 100644
--- a/src/main/twirl/gitbucket/core/admin/usergroup.scala.html
+++ b/src/main/twirl/gitbucket/core/admin/usergroup.scala.html
@@ -75,16 +75,14 @@
     }
 
     // check existence
-    $.post('@context.path/_user/existence', {
-      'userName': userName,
-      'userOnly': true
-    }, function(data, status){
-      if(data == 'true'){
-        addMemberHTML(userName, false);
-      } else {
-        $('#error-members').text('User does not exist.');
-      }
-    });
+    $.post('@context.path/_user/existence', { 'userName': userName },
+      function(data, status){
+        if(data == 'user'){
+          addMemberHTML(userName, false);
+        } else {
+          $('#error-members').text('User does not exist.');
+        }
+      });
   });
 
   $(document).on('click', '.remove', function(){
diff --git a/src/main/twirl/gitbucket/core/settings/collaborators.scala.html b/src/main/twirl/gitbucket/core/settings/collaborators.scala.html
index f20cdc1..f0cf1ec 100644
--- a/src/main/twirl/gitbucket/core/settings/collaborators.scala.html
+++ b/src/main/twirl/gitbucket/core/settings/collaborators.scala.html
@@ -48,15 +48,14 @@
     }
 
     // check existence
-    $.post('@context.path/_user/existence', {
-      'userName': userName
-    }, function(data, status){
-      if(data == 'true'){
-        addCollaboratorHTML(userName, '@Permission.ADMIN.name'); // TODO isGroup
-      } else {
-        $('#error-collaborators').text('User does not exist.');
-      }
-    });
+    $.post('@context.path/_user/existence', { 'userName': userName },
+      function(data, status){
+        if(data != ''){
+          addCollaboratorHTML(userName, '@Permission.ADMIN.name', data == 'group');
+        } else {
+          $('#error-collaborators').text('User does not exist.');
+        }
+      });
   });
 
   $(document).on('click', '.remove', function(){