diff --git a/src/main/scala/gitbucket/core/model/WebHook.scala b/src/main/scala/gitbucket/core/model/WebHook.scala
index 6f89b0e..48de21b 100644
--- a/src/main/scala/gitbucket/core/model/WebHook.scala
+++ b/src/main/scala/gitbucket/core/model/WebHook.scala
@@ -17,11 +17,10 @@
   }
 }
 
-case class WebHookContentType(val code: String, val ctype: String)
+abstract sealed case class WebHookContentType(code: String, ctype: String)
 
 object WebHookContentType {
   object JSON extends WebHookContentType("json", "application/json")
-
   object FORM extends WebHookContentType("form", "application/x-www-form-urlencoded")
 
   val values: Vector[WebHookContentType] = Vector(JSON, FORM)
@@ -43,7 +42,8 @@
 )
 
 object WebHook {
-  sealed class Event(var name: String)
+  abstract sealed class Event(val name: String)
+
   case object CommitComment extends Event("commit_comment")
   case object Create extends Event("create")
   case object Delete extends Event("delete")
@@ -63,9 +63,30 @@
   case object Status extends Event("status")
   case object TeamAdd extends Event("team_add")
   case object Watch extends Event("watch")
+
   object Event{
-    val values = List(CommitComment,Create,Delete,Deployment,DeploymentStatus,Fork,Gollum,IssueComment,Issues,Member,PageBuild,Public,PullRequest,PullRequestReviewComment,Push,Release,Status,TeamAdd,Watch)
-    private val map:Map[String,Event] = values.map(e => e.name -> e).toMap
+    val values = List(
+      CommitComment,
+      Create,
+      Delete,
+      Deployment,
+      DeploymentStatus,
+      Fork,
+      Gollum,
+      IssueComment,
+      Issues,
+      Member,
+      PageBuild,
+      Public,
+      PullRequest,
+      PullRequestReviewComment,
+      Push,
+      Release,
+      Status,
+      TeamAdd,
+      Watch
+    )
+    private val map: Map[String,Event] = values.map(e => e.name -> e).toMap
     def valueOf(name: String): Event = map(name)
     def valueOpt(name: String): Option[Event] = map.get(name)
   }
diff --git a/src/main/scala/gitbucket/core/service/IssuesService.scala b/src/main/scala/gitbucket/core/service/IssuesService.scala
index ef34185..0d729ed 100644
--- a/src/main/scala/gitbucket/core/service/IssuesService.scala
+++ b/src/main/scala/gitbucket/core/service/IssuesService.scala
@@ -455,6 +455,7 @@
           case ("comments", "asc" ) => Some("sort:comments-asc")
           case ("updated" , "desc") => Some("sort:updated-desc")
           case ("updated" , "asc" ) => Some("sort:updated-asc")
+          case x                    => throw new MatchError(x)
         },
         visibility.map(visibility => s"visibility:${visibility}")
       ).flatten ++