diff --git a/src/main/scala/gitbucket/core/controller/AccountController.scala b/src/main/scala/gitbucket/core/controller/AccountController.scala
index 5ddc010..caddeab 100644
--- a/src/main/scala/gitbucket/core/controller/AccountController.scala
+++ b/src/main/scala/gitbucket/core/controller/AccountController.scala
@@ -447,8 +447,8 @@
 
   private def validPublicKey: Constraint = new Constraint(){
     override def validate(name: String, value: String, messages: Messages): Option[String] = SshUtil.str2PublicKey(value) match {
-     case Some(_) => None
-     case None => Some("Key is invalid.")
+     case Some(_) if !getAllKeys().exists(_.publicKey == value) => None
+     case _ => Some("Key is invalid.")
     }
   }