diff --git a/src/main/scala/gitbucket/core/controller/AccountController.scala b/src/main/scala/gitbucket/core/controller/AccountController.scala
index 12ec24e..c0f0212 100644
--- a/src/main/scala/gitbucket/core/controller/AccountController.scala
+++ b/src/main/scala/gitbucket/core/controller/AccountController.scala
@@ -38,7 +38,7 @@
   case class PersonalTokenForm(note: String)
 
   val newForm = mapping(
-    "userName"    -> trim(label("User name"    , text(required, maxlength(100), identifier, uniqueUserName))),
+    "userName"    -> trim(label("User name"    , text(required, maxlength(100), identifier, uniqueUserName, reservedNames))),
     "password"    -> trim(label("Password"     , text(required, maxlength(20)))),
     "fullName"    -> trim(label("Full Name"    , text(required, maxlength(100)))),
     "mailAddress" -> trim(label("Mail Address" , text(required, maxlength(100), uniqueMailAddress()))),
@@ -68,7 +68,7 @@
   case class EditGroupForm(groupName: String, url: Option[String], fileId: Option[String], members: String, clearImage: Boolean)
 
   val newGroupForm = mapping(
-    "groupName" -> trim(label("Group name" ,text(required, maxlength(100), identifier, uniqueUserName))),
+    "groupName" -> trim(label("Group name" ,text(required, maxlength(100), identifier, uniqueUserName, reservedNames))),
     "url"       -> trim(label("URL"        ,optional(text(maxlength(200))))),
     "fileId"    -> trim(label("File ID"    ,optional(text()))),
     "members"   -> trim(label("Members"    ,text(required, members)))
diff --git a/src/main/scala/gitbucket/core/controller/ControllerBase.scala b/src/main/scala/gitbucket/core/controller/ControllerBase.scala
index a336509..891512b 100644
--- a/src/main/scala/gitbucket/core/controller/ControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/ControllerBase.scala
@@ -244,4 +244,12 @@
         .map    { _ => "Mail address is already registered." }
   }
 
+  protected def reservedNames(): Constraint = new Constraint(){
+    override def validate(name: String, value: String, messages: Messages): Option[String] = if(value == "git"){
+      Some(s"${value} is reserved")
+    }else{
+      None
+    }
+  }
+
 }
diff --git a/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala b/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala
index dd37a34..57f1495 100644
--- a/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala
+++ b/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala
@@ -105,7 +105,7 @@
 
 
   val newUserForm = mapping(
-    "userName"    -> trim(label("Username"     ,text(required, maxlength(100), identifier, uniqueUserName))),
+    "userName"    -> trim(label("Username"     ,text(required, maxlength(100), identifier, uniqueUserName, reservedNames))),
     "password"    -> trim(label("Password"     ,text(required, maxlength(20)))),
     "fullName"    -> trim(label("Full Name"    ,text(required, maxlength(100)))),
     "mailAddress" -> trim(label("Mail Address" ,text(required, maxlength(100), uniqueMailAddress()))),
@@ -127,7 +127,7 @@
   )(EditUserForm.apply)
 
   val newGroupForm = mapping(
-    "groupName" -> trim(label("Group name" ,text(required, maxlength(100), identifier, uniqueUserName))),
+    "groupName" -> trim(label("Group name" ,text(required, maxlength(100), identifier, uniqueUserName, reservedNames))),
     "url"       -> trim(label("URL"        ,optional(text(maxlength(200))))),
     "fileId"    -> trim(label("File ID"    ,optional(text()))),
     "members"   -> trim(label("Members"    ,text(required, members)))