diff --git a/src/main/scala/gitbucket/core/GitBucketCoreModule.scala b/src/main/scala/gitbucket/core/GitBucketCoreModule.scala
index b4c0df1..3d63b0c 100644
--- a/src/main/scala/gitbucket/core/GitBucketCoreModule.scala
+++ b/src/main/scala/gitbucket/core/GitBucketCoreModule.scala
@@ -12,7 +12,7 @@
 import io.github.gitbucket.solidbase.Solidbase
 import io.github.gitbucket.solidbase.migration.{LiquibaseMigration, Migration, SqlMigration}
 import io.github.gitbucket.solidbase.model.{Module, Version}
-import org.json4s.NoTypeHints
+import org.json4s.{Formats, NoTypeHints}
 import org.json4s.jackson.Serialization
 import org.json4s.jackson.Serialization.write
 
@@ -85,7 +85,7 @@
         "4.34.0",
         new Migration() {
           override def migrate(moduleId: String, version: String, context: util.Map[String, AnyRef]): Unit = {
-            implicit val formats = Serialization.formats(NoTypeHints)
+            implicit val formats: Formats = Serialization.formats(NoTypeHints)
             import JDBCUtil._
 
             val conn = context.get(Solidbase.CONNECTION).asInstanceOf[Connection]
diff --git a/src/main/scala/gitbucket/core/api/ApiBranchProtection.scala b/src/main/scala/gitbucket/core/api/ApiBranchProtection.scala
index 1c3eac5..96e2a9d 100644
--- a/src/main/scala/gitbucket/core/api/ApiBranchProtection.scala
+++ b/src/main/scala/gitbucket/core/api/ApiBranchProtection.scala
@@ -66,7 +66,7 @@
       }
   }
 
-  implicit val enforcementLevelSerializer = new CustomSerializer[EnforcementLevel](
+  implicit val enforcementLevelSerializer: CustomSerializer[EnforcementLevel] = new CustomSerializer[EnforcementLevel](
     format =>
       (
         {
diff --git a/src/main/scala/gitbucket/core/controller/ControllerBase.scala b/src/main/scala/gitbucket/core/controller/ControllerBase.scala
index e5d3d0c..dce356c 100644
--- a/src/main/scala/gitbucket/core/controller/ControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/ControllerBase.scala
@@ -28,6 +28,7 @@
 import org.eclipse.jgit.treewalk._
 import org.apache.commons.io.IOUtils
 import org.slf4j.LoggerFactory
+import org.json4s.Formats
 
 /**
  * Provides generic features for controller implementations.
@@ -43,7 +44,7 @@
 
   private val logger = LoggerFactory.getLogger(getClass)
 
-  implicit val jsonFormats = gitbucket.core.api.JsonFormat.jsonFormats
+  implicit val jsonFormats: Formats = gitbucket.core.api.JsonFormat.jsonFormats
 
   before("/api/v3/*") {
     contentType = formats("json")
diff --git a/src/main/scala/gitbucket/core/controller/FileUploadController.scala b/src/main/scala/gitbucket/core/controller/FileUploadController.scala
index 69cc725..f3a0383 100644
--- a/src/main/scala/gitbucket/core/controller/FileUploadController.scala
+++ b/src/main/scala/gitbucket/core/controller/FileUploadController.scala
@@ -18,6 +18,7 @@
 
 import scala.util.Using
 import gitbucket.core.service.SystemSettingsService
+import slick.jdbc.JdbcBackend.Session
 
 /**
  * Provides Ajax based file upload functionality.
@@ -178,7 +179,7 @@
   }
 
   private def onlyWikiEditable(owner: String, repository: String, loginAccount: Account)(action: => Any): Any = {
-    implicit val session = Database.getSession(request)
+    implicit val session: Session = Database.getSession(request)
     getRepository(owner, repository) match {
       case Some(x) =>
         x.repository.options.wikiOption match {
diff --git a/src/main/scala/gitbucket/core/model/AccountWebHook.scala b/src/main/scala/gitbucket/core/model/AccountWebHook.scala
index 7aa8edf..0c6d7a6 100644
--- a/src/main/scala/gitbucket/core/model/AccountWebHook.scala
+++ b/src/main/scala/gitbucket/core/model/AccountWebHook.scala
@@ -3,7 +3,7 @@
 trait AccountWebHookComponent extends TemplateComponent { self: Profile =>
   import profile.api._
 
-  private implicit val whContentTypeColumnType =
+  private implicit val whContentTypeColumnType: BaseColumnType[WebHookContentType] =
     MappedColumnType.base[WebHookContentType, String](whct => whct.code, code => WebHookContentType.valueOf(code))
 
   lazy val AccountWebHooks = TableQuery[AccountWebHooks]
diff --git a/src/main/scala/gitbucket/core/model/CommitStatus.scala b/src/main/scala/gitbucket/core/model/CommitStatus.scala
index 1e605bc..1e2beb0 100644
--- a/src/main/scala/gitbucket/core/model/CommitStatus.scala
+++ b/src/main/scala/gitbucket/core/model/CommitStatus.scala
@@ -4,7 +4,8 @@
   import profile.api._
   import self._
 
-  implicit val commitStateColumnType = MappedColumnType.base[CommitState, String](b => b.name, i => CommitState(i))
+  implicit val commitStateColumnType: BaseColumnType[CommitState] =
+    MappedColumnType.base[CommitState, String](b => b.name, i => CommitState(i))
 
   lazy val CommitStatuses = TableQuery[CommitStatuses]
   class CommitStatuses(tag: Tag) extends Table[CommitStatus](tag, "COMMIT_STATUS") with CommitTemplate {
diff --git a/src/main/scala/gitbucket/core/model/Profile.scala b/src/main/scala/gitbucket/core/model/Profile.scala
index 75ed43f..5adc312 100644
--- a/src/main/scala/gitbucket/core/model/Profile.scala
+++ b/src/main/scala/gitbucket/core/model/Profile.scala
@@ -10,15 +10,17 @@
   /**
    * java.util.Date Mapped Column Types
    */
-  implicit val dateColumnType = MappedColumnType.base[java.util.Date, java.sql.Timestamp](
-    d => new java.sql.Timestamp(d.getTime),
-    t => new java.util.Date(t.getTime)
-  )
+  implicit val dateColumnType: BaseColumnType[java.util.Date] =
+    MappedColumnType.base[java.util.Date, java.sql.Timestamp](
+      d => new java.sql.Timestamp(d.getTime),
+      t => new java.util.Date(t.getTime)
+    )
 
   /**
    * WebHookBase.Event Column Types
    */
-  implicit val eventColumnType = MappedColumnType.base[WebHook.Event, String](_.name, WebHook.Event.valueOf(_))
+  implicit val eventColumnType: BaseColumnType[WebHook.Event] =
+    MappedColumnType.base[WebHook.Event, String](_.name, WebHook.Event.valueOf(_))
 
   /**
    * Extends Column to add conditional condition
diff --git a/src/main/scala/gitbucket/core/model/RepositoryWebHook.scala b/src/main/scala/gitbucket/core/model/RepositoryWebHook.scala
index 5301c18..e2f7702 100644
--- a/src/main/scala/gitbucket/core/model/RepositoryWebHook.scala
+++ b/src/main/scala/gitbucket/core/model/RepositoryWebHook.scala
@@ -3,7 +3,7 @@
 trait RepositoryWebHookComponent extends TemplateComponent { self: Profile =>
   import profile.api._
 
-  implicit val whContentTypeColumnType =
+  implicit val whContentTypeColumnType: BaseColumnType[WebHookContentType] =
     MappedColumnType.base[WebHookContentType, String](whct => whct.code, code => WebHookContentType.valueOf(code))
 
   lazy val RepositoryWebHooks = TableQuery[RepositoryWebHooks]
diff --git a/src/main/scala/gitbucket/core/service/ActivityService.scala b/src/main/scala/gitbucket/core/service/ActivityService.scala
index 4246440..24f5821 100644
--- a/src/main/scala/gitbucket/core/service/ActivityService.scala
+++ b/src/main/scala/gitbucket/core/service/ActivityService.scala
@@ -22,7 +22,7 @@
 trait ActivityService {
   self: RequestCache =>
 
-  private implicit val formats = Serialization.formats(NoTypeHints)
+  private implicit val formats: Formats = Serialization.formats(NoTypeHints)
 
   private def writeLog(activity: Activity): Unit = {
     Using.resource(new FileOutputStream(ActivityLog, true)) { out =>
diff --git a/src/main/scala/gitbucket/core/servlet/ApiAuthenticationFilter.scala b/src/main/scala/gitbucket/core/servlet/ApiAuthenticationFilter.scala
index dfda603..5fc3554 100644
--- a/src/main/scala/gitbucket/core/servlet/ApiAuthenticationFilter.scala
+++ b/src/main/scala/gitbucket/core/servlet/ApiAuthenticationFilter.scala
@@ -19,8 +19,9 @@
   override def destroy(): Unit = {}
 
   override def doFilter(req: ServletRequest, res: ServletResponse, chain: FilterChain): Unit = {
-    implicit val request = req.asInstanceOf[HttpServletRequest]
-    implicit val session = req.getAttribute(Keys.Request.DBSession).asInstanceOf[slick.jdbc.JdbcBackend#Session]
+    implicit val request: HttpServletRequest = req.asInstanceOf[HttpServletRequest]
+    implicit val session: slick.jdbc.JdbcBackend#Session =
+      req.getAttribute(Keys.Request.DBSession).asInstanceOf[slick.jdbc.JdbcBackend#Session]
     val response = res.asInstanceOf[HttpServletResponse]
     Option(request.getHeader("Authorization"))
       .map {
diff --git a/src/main/scala/gitbucket/core/servlet/GitLfsTransferServlet.scala b/src/main/scala/gitbucket/core/servlet/GitLfsTransferServlet.scala
index 17f1a34..64349bc 100644
--- a/src/main/scala/gitbucket/core/servlet/GitLfsTransferServlet.scala
+++ b/src/main/scala/gitbucket/core/servlet/GitLfsTransferServlet.scala
@@ -6,6 +6,7 @@
 
 import gitbucket.core.util.{FileUtil, StringUtil}
 import org.apache.commons.io.{FileUtils, IOUtils}
+import org.json4s.Formats
 import org.json4s.jackson.Serialization._
 import org.apache.http.HttpStatus
 
@@ -17,7 +18,7 @@
  */
 class GitLfsTransferServlet extends HttpServlet {
 
-  private implicit val jsonFormats = gitbucket.core.api.JsonFormat.jsonFormats
+  private implicit val jsonFormats: Formats = gitbucket.core.api.JsonFormat.jsonFormats
   private val LongObjectIdLength = 32
   private val LongObjectIdStringLength = LongObjectIdLength * 2
 
diff --git a/src/main/scala/gitbucket/core/servlet/GitRepositoryServlet.scala b/src/main/scala/gitbucket/core/servlet/GitRepositoryServlet.scala
index 8d06399..e082d31 100644
--- a/src/main/scala/gitbucket/core/servlet/GitRepositoryServlet.scala
+++ b/src/main/scala/gitbucket/core/servlet/GitRepositoryServlet.scala
@@ -6,6 +6,7 @@
 
 import scala.util.Using
 import gitbucket.core.api
+import gitbucket.core.api.JsonFormat.Context
 import gitbucket.core.model.WebHook
 import gitbucket.core.plugin.{GitRepositoryRouting, PluginRegistry}
 import gitbucket.core.service.IssuesService.IssueSearchCondition
@@ -42,6 +43,7 @@
 import javax.servlet.http.{HttpServletRequest, HttpServletResponse}
 import org.eclipse.jgit.diff.DiffEntry.ChangeType
 import org.eclipse.jgit.internal.storage.file.FileRepository
+import org.json4s.Formats
 import org.json4s.jackson.Serialization._
 
 /**
@@ -53,7 +55,7 @@
 class GitRepositoryServlet extends GitServlet with SystemSettingsService {
 
   private val logger = LoggerFactory.getLogger(classOf[GitRepositoryServlet])
-  private implicit val jsonFormats = gitbucket.core.api.JsonFormat.jsonFormats
+  private implicit val jsonFormats: Formats = gitbucket.core.api.JsonFormat.jsonFormats
 
   override def init(config: ServletConfig): Unit = {
     setReceivePackFactory(new GitBucketReceivePackFactory())
@@ -293,7 +295,7 @@
           val pushedIds = scala.collection.mutable.Set[String]()
           commands.asScala.foreach { command =>
             logger.debug(s"commandType: ${command.getType}, refName: ${command.getRefName}")
-            implicit val apiContext = api.JsonFormat.Context(baseUrl, sshUrl)
+            implicit val apiContext: Context = api.JsonFormat.Context(baseUrl, sshUrl)
             val refName = command.getRefName.split("/")
             val branchName = refName.drop(2).mkString("/")
             val commits = if (refName(1) == "tags") {
@@ -469,7 +471,7 @@
     Database() withTransaction { implicit session =>
       try {
         commands.asScala.headOption.foreach { command =>
-          implicit val apiContext = api.JsonFormat.Context(baseUrl, sshUrl)
+          implicit val apiContext: Context = api.JsonFormat.Context(baseUrl, sshUrl)
           val refName = command.getRefName.split("/")
           val commitIds = if (refName(1) == "tags") {
             None
diff --git a/src/main/scala/gitbucket/core/util/JGitUtil.scala b/src/main/scala/gitbucket/core/util/JGitUtil.scala
index e6836c8..3e0063c 100644
--- a/src/main/scala/gitbucket/core/util/JGitUtil.scala
+++ b/src/main/scala/gitbucket/core/util/JGitUtil.scala
@@ -38,7 +38,7 @@
 
   private val logger = LoggerFactory.getLogger(JGitUtil.getClass)
 
-  implicit val objectDatabaseReleasable = new Releasable[ObjectDatabase] {
+  implicit val objectDatabaseReleasable: Releasable[ObjectDatabase] = new Releasable[ObjectDatabase] {
     override def release(resource: ObjectDatabase): Unit = resource.close()
   }
 
diff --git a/src/main/scala/gitbucket/core/view/helpers.scala b/src/main/scala/gitbucket/core/view/helpers.scala
index 9828128..3b72130 100644
--- a/src/main/scala/gitbucket/core/view/helpers.scala
+++ b/src/main/scala/gitbucket/core/view/helpers.scala
@@ -11,6 +11,7 @@
 import gitbucket.core.service.{RepositoryService, RequestCache}
 import gitbucket.core.util.{FileUtil, JGitUtil, StringUtil}
 import org.apache.commons.codec.digest.DigestUtils
+import org.json4s.Formats
 import play.twirl.api.{Html, HtmlFormat}
 
 /**
@@ -387,7 +388,7 @@
    * Render a given object as the JSON string.
    */
   def json(obj: AnyRef): String = {
-    implicit val formats = org.json4s.DefaultFormats
+    implicit val formats: Formats = org.json4s.DefaultFormats
     org.json4s.jackson.Serialization.write(obj)
   }
 
@@ -472,7 +473,7 @@
   def diff(jsonString: String): Html = {
     import org.json4s._
     import org.json4s.jackson.JsonMethods._
-    implicit val formats = DefaultFormats
+    implicit val formats: Formats = DefaultFormats
 
     val diff = parse(jsonString).extract[Seq[CommentDiffLine]]