diff --git a/src/main/scala/gitbucket/core/util/Implicits.scala b/src/main/scala/gitbucket/core/util/Implicits.scala
index d93ebe2..77767a3 100644
--- a/src/main/scala/gitbucket/core/util/Implicits.scala
+++ b/src/main/scala/gitbucket/core/util/Implicits.scala
@@ -24,7 +24,7 @@
 
   implicit def context2ApiJsonFormatContext(implicit context: Context): JsonFormat.Context = JsonFormat.Context(context.baseUrl)
 
-  implicit class RichSeq[A](seq: Seq[A]) {
+  implicit class RichSeq[A](private val seq: Seq[A]) extends AnyVal {
 
     def splitWith(condition: (A, A) => Boolean): Seq[Seq[A]] = split(seq)(condition)
 
@@ -40,7 +40,7 @@
       }
   }
 
-  implicit class RichString(value: String){
+  implicit class RichString(private val value: String) extends AnyVal {
     def replaceBy(regex: Regex)(replace: Regex.MatchData => Option[String]): String = {
       val sb = new StringBuilder()
       var i = 0
@@ -63,7 +63,7 @@
     }
   }
 
-  implicit class RichRequest(request: HttpServletRequest){
+  implicit class RichRequest(private val request: HttpServletRequest) extends AnyVal {
 
     def paths: Array[String] = (request.getRequestURI.substring(request.getContextPath.length + 1) match{
       case path if path.startsWith("api/v3/repos/") => path.substring(13/* "/api/v3/repos".length */)
@@ -84,7 +84,7 @@
     }
   }
 
-  implicit class RichSession(session: HttpSession){
+  implicit class RichSession(private val session: HttpSession) extends AnyVal {
     def getAndRemove[T](key: String): Option[T] = {
       val value = session.getAttribute(key).asInstanceOf[T]
       if(value == null){
diff --git a/src/main/scala/gitbucket/core/util/JDBCUtil.scala b/src/main/scala/gitbucket/core/util/JDBCUtil.scala
index edc41ec..f94b341 100644
--- a/src/main/scala/gitbucket/core/util/JDBCUtil.scala
+++ b/src/main/scala/gitbucket/core/util/JDBCUtil.scala
@@ -16,7 +16,7 @@
  */
 object JDBCUtil {
 
-  implicit class RichConnection(conn: Connection){
+  implicit class RichConnection(private val conn: Connection) extends AnyVal {
 
     def update(sql: String, params: Any*): Int = {
       execute(sql, params: _*){ stmt =>
@@ -214,8 +214,6 @@
       tsort(edges).toSeq
     }
 
-    case class TableDependency(tableName: String, children: Seq[String])
-
 
     def tsort[A](edges: Traversable[(A, A)]): Iterable[A] = {
       @tailrec
@@ -236,4 +234,6 @@
     }
   }
 
+  private case class TableDependency(tableName: String, children: Seq[String])
+
 }
diff --git a/src/main/scala/gitbucket/core/view/helpers.scala b/src/main/scala/gitbucket/core/view/helpers.scala
index d29248a..beff9d5 100644
--- a/src/main/scala/gitbucket/core/view/helpers.scala
+++ b/src/main/scala/gitbucket/core/view/helpers.scala
@@ -161,7 +161,7 @@
     }
 
   import scala.util.matching.Regex._
-  implicit class RegexReplaceString(s: String) {
+  implicit class RegexReplaceString(private val s: String) extends AnyVal {
     def replaceAll(pattern: String, replacer: (Match) => String): String = {
       pattern.r.replaceAllIn(s, (m: Match) => replacer(m).replace("$", "\\$"))
     }
@@ -297,7 +297,7 @@
   /**
    * Implicit conversion to add mkHtml() to Seq[Html].
    */
-  implicit class RichHtmlSeq(seq: Seq[Html]) {
+  implicit class RichHtmlSeq(private val seq: Seq[Html]) extends AnyVal {
     def mkHtml(separator: String) = Html(seq.mkString(separator))
     def mkHtml(separator: scala.xml.Elem) = Html(seq.mkString(separator.toString))
   }