diff --git a/build.sbt b/build.sbt
index 77a683d..7186285 100644
--- a/build.sbt
+++ b/build.sbt
@@ -4,7 +4,7 @@
 val Organization = "io.github.gitbucket"
 val Name = "gitbucket"
 val GitBucketVersion = "4.19.0-SNAPSHOT"
-val ScalatraVersion = "2.5.3"
+val ScalatraVersion = "2.6.0-SNAPSHOT"
 val JettyVersion = "9.4.7.v20170914"
 
 lazy val root = (project in file(".")).enablePlugins(SbtTwirl, ScalatraPlugin, JRebelPlugin).settings(
@@ -30,8 +30,8 @@
   "org.eclipse.jgit"                %  "org.eclipse.jgit.archive"     % "4.9.0.201710071750-r",
   "org.scalatra"                    %% "scalatra"                     % ScalatraVersion,
   "org.scalatra"                    %% "scalatra-json"                % ScalatraVersion,
+  "org.scalatra"                    %% "scalatra-forms"               % ScalatraVersion,
   "org.json4s"                      %% "json4s-jackson"               % "3.5.1",
-  "io.github.gitbucket"             %% "scalatra-forms"               % "1.1.0",
   "commons-io"                      %  "commons-io"                   % "2.5",
   "io.github.gitbucket"             %  "solidbase"                    % "1.0.2",
   "io.github.gitbucket"             %  "markedj"                      % "1.0.15",
diff --git a/src/main/scala/gitbucket/core/controller/AccountController.scala b/src/main/scala/gitbucket/core/controller/AccountController.scala
index d0b22db..f2959ca 100644
--- a/src/main/scala/gitbucket/core/controller/AccountController.scala
+++ b/src/main/scala/gitbucket/core/controller/AccountController.scala
@@ -12,10 +12,10 @@
 import gitbucket.core.util.Implicits._
 import gitbucket.core.util.StringUtil._
 import gitbucket.core.util._
-import io.github.gitbucket.scalatra.forms._
 import org.apache.commons.io.FileUtils
 import org.scalatra.i18n.Messages
 import org.scalatra.BadRequest
+import org.scalatra.forms._
 
 class AccountController extends AccountControllerBase
   with AccountService with RepositoryService with ActivityService with WikiService with LabelsService with SshKeyService
@@ -137,16 +137,17 @@
   }
 
   private def accountWebhookEvents = new ValueType[Set[WebHook.Event]]{
-    def convert(name: String, params: Map[String, String], messages: Messages): Set[WebHook.Event] = {
+    def convert(name: String, params: Map[String, Seq[String]], messages: Messages): Set[WebHook.Event] = {
       WebHook.Event.values.flatMap { t =>
         params.get(name + "." + t.name).map(_ => t)
       }.toSet
     }
-    def validate(name: String, params: Map[String, String], messages: Messages): Seq[(String, String)] = if(convert(name,params,messages).isEmpty){
-      Seq(name -> messages("error.required").format(name))
-    } else {
-      Nil
-    }
+    def validate(name: String, params: Map[String, Seq[String]], messages: Messages): Seq[(String, String)] =
+      if(convert(name, params, messages).isEmpty){
+        Seq(name -> messages("error.required").format(name))
+      } else {
+        Nil
+      }
   }
 
 
@@ -635,9 +636,9 @@
   }
 
   private def uniqueRepository: Constraint = new Constraint(){
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Option[String] =
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Option[String] =
       params.get("owner").flatMap { userName =>
-        getRepositoryNamesOfUser(userName).find(_ == value).map(_ => "Repository already exists.")
+        getRepositoryNamesOfUser(userName.head).find(_ == value).map(_ => "Repository already exists.")
       }
   }
 
diff --git a/src/main/scala/gitbucket/core/controller/ControllerBase.scala b/src/main/scala/gitbucket/core/controller/ControllerBase.scala
index 928e5f6..4948c43 100644
--- a/src/main/scala/gitbucket/core/controller/ControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/ControllerBase.scala
@@ -9,12 +9,11 @@
 import gitbucket.core.util.Directory._
 import gitbucket.core.util.Implicits._
 import gitbucket.core.util._
-import gitbucket.core.util.JGitUtil._
-import io.github.gitbucket.scalatra.forms._
 import org.json4s._
 import org.scalatra._
 import org.scalatra.i18n._
 import org.scalatra.json._
+import org.scalatra.forms._
 import javax.servlet.http.{HttpServletRequest, HttpServletResponse}
 import javax.servlet.{FilterChain, ServletRequest, ServletResponse}
 
@@ -32,7 +31,7 @@
  * Provides generic features for controller implementations.
  */
 abstract class ControllerBase extends ScalatraFilter
-  with ClientSideValidationFormSupport with JacksonJsonSupport with I18nSupport with FlashMapSupport with Validations
+  with ValidationSupport with JacksonJsonSupport with I18nSupport with FlashMapSupport with Validations
   with SystemSettingsService {
 
   private val logger = LoggerFactory.getLogger(getClass)
@@ -177,7 +176,7 @@
   protected def trim2[T](valueType: SingleValueType[T]): SingleValueType[T] = new SingleValueType[T](){
     def convert(value: String, messages: Messages): T = valueType.convert(trim(value), messages)
 
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Seq[(String, String)] =
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Seq[(String, String)] =
       valueType.validate(name, trim(value), params, messages)
 
     private def trim(value: String): String = if(value == null) null else value.replace("\r\n", "").trim
@@ -315,7 +314,7 @@
   }
 
   protected def uniqueMailAddress(paramName: String = ""): Constraint = new Constraint(){
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Option[String] =
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Option[String] =
       getAccountByMailAddress(value, true)
         .filter { x => if(paramName.isEmpty) true else Some(x.userName) != params.get(paramName) }
         .map    { _ => "Mail address is already registered." }
diff --git a/src/main/scala/gitbucket/core/controller/FileUploadController.scala b/src/main/scala/gitbucket/core/controller/FileUploadController.scala
index 7bf8408..6a45d9d 100644
--- a/src/main/scala/gitbucket/core/controller/FileUploadController.scala
+++ b/src/main/scala/gitbucket/core/controller/FileUploadController.scala
@@ -1,7 +1,6 @@
 package gitbucket.core.controller
 
 import gitbucket.core.model.Account
-import gitbucket.core.service.RepositoryService.RepositoryInfo
 import gitbucket.core.service.{AccountService, RepositoryService}
 import gitbucket.core.servlet.Database
 import gitbucket.core.util._
diff --git a/src/main/scala/gitbucket/core/controller/IndexController.scala b/src/main/scala/gitbucket/core/controller/IndexController.scala
index a4cf49f..9209ab4 100644
--- a/src/main/scala/gitbucket/core/controller/IndexController.scala
+++ b/src/main/scala/gitbucket/core/controller/IndexController.scala
@@ -6,7 +6,7 @@
 import gitbucket.core.util.Implicits._
 import gitbucket.core.util.SyntaxSugars._
 import gitbucket.core.util.{Keys, LDAPUtil, ReferrerAuthenticator, UsersAuthenticator}
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.scalatra.Ok
 
 
diff --git a/src/main/scala/gitbucket/core/controller/IssuesController.scala b/src/main/scala/gitbucket/core/controller/IssuesController.scala
index e24cc55..4472863 100644
--- a/src/main/scala/gitbucket/core/controller/IssuesController.scala
+++ b/src/main/scala/gitbucket/core/controller/IssuesController.scala
@@ -8,7 +8,7 @@
 import gitbucket.core.util._
 import gitbucket.core.view
 import gitbucket.core.view.Markdown
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.scalatra.{BadRequest, Ok}
 
 
diff --git a/src/main/scala/gitbucket/core/controller/LabelsController.scala b/src/main/scala/gitbucket/core/controller/LabelsController.scala
index 08c0aaa..d0d82d4 100644
--- a/src/main/scala/gitbucket/core/controller/LabelsController.scala
+++ b/src/main/scala/gitbucket/core/controller/LabelsController.scala
@@ -4,7 +4,7 @@
 import gitbucket.core.service.{RepositoryService, AccountService, IssuesService, LabelsService}
 import gitbucket.core.util.{ReferrerAuthenticator, WritableUsersAuthenticator}
 import gitbucket.core.util.Implicits._
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.scalatra.i18n.Messages
 import org.scalatra.Ok
 
@@ -82,11 +82,11 @@
   }
 
   private def uniqueLabelName: Constraint = new Constraint(){
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Option[String] = {
-      val owner = params("owner")
-      val repository = params("repository")
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Option[String] = {
+      val owner = params("owner").head
+      val repository = params("repository").head
       params.get("labelId").map { labelId =>
-        getLabel(owner, repository, value).filter(_.labelId != labelId.toInt).map(_ => "Name has already been taken.")
+        getLabel(owner, repository, value).filter(_.labelId != labelId.head.toInt).map(_ => "Name has already been taken.")
       }.getOrElse {
         getLabel(owner, repository, value).map(_ => "Name has already been taken.")
       }
diff --git a/src/main/scala/gitbucket/core/controller/MilestonesController.scala b/src/main/scala/gitbucket/core/controller/MilestonesController.scala
index de81c73..b373b1b 100644
--- a/src/main/scala/gitbucket/core/controller/MilestonesController.scala
+++ b/src/main/scala/gitbucket/core/controller/MilestonesController.scala
@@ -4,7 +4,7 @@
 import gitbucket.core.service.{RepositoryService, MilestonesService, AccountService}
 import gitbucket.core.util.{ReferrerAuthenticator, WritableUsersAuthenticator}
 import gitbucket.core.util.Implicits._
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 
 class MilestonesController extends MilestonesControllerBase
   with MilestonesService with RepositoryService with AccountService
diff --git a/src/main/scala/gitbucket/core/controller/PrioritiesController.scala b/src/main/scala/gitbucket/core/controller/PrioritiesController.scala
index e0e010a..340065f 100644
--- a/src/main/scala/gitbucket/core/controller/PrioritiesController.scala
+++ b/src/main/scala/gitbucket/core/controller/PrioritiesController.scala
@@ -4,7 +4,7 @@
 import gitbucket.core.service.{RepositoryService, AccountService, IssuesService, PrioritiesService}
 import gitbucket.core.util.{ReferrerAuthenticator, WritableUsersAuthenticator}
 import gitbucket.core.util.Implicits._
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.scalatra.i18n.Messages
 import org.scalatra.Ok
 
@@ -98,11 +98,11 @@
   }
 
   private def uniquePriorityName: Constraint = new Constraint(){
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Option[String] = {
-      val owner = params("owner")
-      val repository = params("repository")
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Option[String] = {
+      val owner = params("owner").head
+      val repository = params("repository").head
       params.get("priorityId").map { priorityId =>
-        getPriority(owner, repository, value).filter(_.priorityId != priorityId.toInt).map(_ => "Name has already been taken.")
+        getPriority(owner, repository, value).filter(_.priorityId != priorityId.head.toInt).map(_ => "Name has already been taken.")
       }.getOrElse {
         getPriority(owner, repository, value).map(_ => "Name has already been taken.")
       }
diff --git a/src/main/scala/gitbucket/core/controller/PullRequestsController.scala b/src/main/scala/gitbucket/core/controller/PullRequestsController.scala
index 839da3f..e8c7208 100644
--- a/src/main/scala/gitbucket/core/controller/PullRequestsController.scala
+++ b/src/main/scala/gitbucket/core/controller/PullRequestsController.scala
@@ -13,7 +13,7 @@
 import gitbucket.core.util.Directory._
 import gitbucket.core.util.Implicits._
 import gitbucket.core.util._
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.eclipse.jgit.api.Git
 import org.eclipse.jgit.lib.PersonIdent
 
diff --git a/src/main/scala/gitbucket/core/controller/RepositorySettingsController.scala b/src/main/scala/gitbucket/core/controller/RepositorySettingsController.scala
index a61776b..df8a0a9 100644
--- a/src/main/scala/gitbucket/core/controller/RepositorySettingsController.scala
+++ b/src/main/scala/gitbucket/core/controller/RepositorySettingsController.scala
@@ -9,7 +9,7 @@
 import gitbucket.core.util.SyntaxSugars._
 import gitbucket.core.util.Implicits._
 import gitbucket.core.util.Directory._
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.apache.commons.io.FileUtils
 import org.scalatra.i18n.Messages
 import org.eclipse.jgit.api.Git
@@ -425,12 +425,12 @@
   }
 
   private def webhookEvents = new ValueType[Set[WebHook.Event]]{
-    def convert(name: String, params: Map[String, String], messages: Messages): Set[WebHook.Event] = {
+    def convert(name: String, params: Map[String, Seq[String]], messages: Messages): Set[WebHook.Event] = {
       WebHook.Event.values.flatMap { t =>
         params.get(name + "." + t.name).map(_ => t)
       }.toSet
     }
-    def validate(name: String, params: Map[String, String], messages: Messages): Seq[(String, String)] = if(convert(name,params,messages).isEmpty){
+    def validate(name: String, params: Map[String, Seq[String]], messages: Messages): Seq[(String, String)] = if(convert(name,params,messages).isEmpty){
       Seq(name -> messages("error.required").format(name))
     } else {
       Nil
@@ -456,10 +456,10 @@
    * Duplicate check for the rename repository name.
    */
   private def renameRepositoryName: Constraint = new Constraint(){
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Option[String] =
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Option[String] =
       params.get("repository").filter(_ != value).flatMap { _ =>
         params.get("owner").flatMap { userName =>
-          getRepositoryNamesOfUser(userName).find(_ == value).map(_ => "Repository already exists.")
+          getRepositoryNamesOfUser(userName.head).find(_ == value).map(_ => "Repository already exists.")
         }
       }
   }
@@ -468,7 +468,7 @@
    *
    */
   private def featureOption: Constraint = new Constraint(){
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Option[String] =
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Option[String] =
       if(Seq("DISABLE", "PRIVATE", "PUBLIC", "ALL").contains(value)) None else Some("Option is invalid.")
   }
 
diff --git a/src/main/scala/gitbucket/core/controller/RepositoryViewerController.scala b/src/main/scala/gitbucket/core/controller/RepositoryViewerController.scala
index bf529cf..c425064 100644
--- a/src/main/scala/gitbucket/core/controller/RepositoryViewerController.scala
+++ b/src/main/scala/gitbucket/core/controller/RepositoryViewerController.scala
@@ -17,7 +17,7 @@
 import gitbucket.core.service.WebHookService._
 import gitbucket.core.view
 import gitbucket.core.view.helpers
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.apache.commons.io.FileUtils
 import org.eclipse.jgit.api.{ArchiveCommand, Git}
 import org.eclipse.jgit.archive.{TgzFormat, ZipFormat}
diff --git a/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala b/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala
index 1485d56..e306017 100644
--- a/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala
+++ b/src/main/scala/gitbucket/core/controller/SystemSettingsController.scala
@@ -12,7 +12,7 @@
 import gitbucket.core.util.SyntaxSugars._
 import gitbucket.core.util.Directory._
 import gitbucket.core.util.StringUtil._
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.apache.commons.io.{FileUtils, IOUtils}
 import org.scalatra.i18n.Messages
 import com.github.zafarkhaja.semver.{Version => Semver}
diff --git a/src/main/scala/gitbucket/core/controller/ValidationSupport.scala b/src/main/scala/gitbucket/core/controller/ValidationSupport.scala
new file mode 100644
index 0000000..9c3e02b
--- /dev/null
+++ b/src/main/scala/gitbucket/core/controller/ValidationSupport.scala
@@ -0,0 +1,91 @@
+package gitbucket.core.controller
+
+import org.json4s.{JField, JObject, JString}
+import org.scalatra._
+import org.scalatra.json._
+import org.scalatra.forms._
+import org.scalatra.i18n.I18nSupport
+import org.scalatra.servlet.ServletBase
+
+/**
+ * Extends scalatra-forms to support the client-side validation and Ajax requests as well.
+ */
+trait ValidationSupport extends FormSupport { self: ServletBase with JacksonJsonSupport with I18nSupport =>
+
+  def get[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    registerValidate(path, form)
+    get(path){
+      validate(form)(errors => BadRequest(), form => action(form))
+    }
+  }
+
+  def post[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    registerValidate(path, form)
+    post(path){
+      validate(form)(errors => BadRequest(), form => action(form))
+    }
+  }
+
+  def put[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    registerValidate(path, form)
+    put(path){
+      validate(form)(errors => BadRequest(), form => action(form))
+    }
+  }
+
+  def delete[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    registerValidate(path, form)
+    delete(path){
+      validate(form)(errors => BadRequest(), form => action(form))
+    }
+  }
+
+  def ajaxGet[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    get(path){
+      validate(form)(errors => ajaxError(errors), form => action(form))
+    }
+  }
+
+  def ajaxPost[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    post(path){
+      validate(form)(errors => ajaxError(errors), form => action(form))
+    }
+  }
+
+  def ajaxDelete[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    delete(path){
+      validate(form)(errors => ajaxError(errors), form => action(form))
+    }
+  }
+
+  def ajaxPut[T](path: String, form: ValueType[T])(action: T => Any): Route = {
+    put(path){
+      validate(form)(errors => ajaxError(errors), form => action(form))
+    }
+  }
+
+  private def registerValidate[T](path: String, form: ValueType[T]) = {
+    post(path.replaceFirst("/$", "") + "/validate"){
+      contentType = "application/json"
+      toJson(form.validate("", multiParams, messages))
+    }
+  }
+
+  /**
+   * Responds errors for ajax requests.
+   */
+  private def ajaxError(errors: Seq[(String, String)]): JObject = {
+    status = 400
+    contentType = "application/json"
+    toJson(errors)
+  }
+
+  /**
+   * Converts errors to JSON.
+   */
+  private def toJson(errors: Seq[(String, String)]): JObject =
+    JObject(errors.map { case (key, value) =>
+      JField(key, JString(value))
+    }.toList)
+
+}
diff --git a/src/main/scala/gitbucket/core/controller/WikiController.scala b/src/main/scala/gitbucket/core/controller/WikiController.scala
index f034602..b212b81 100644
--- a/src/main/scala/gitbucket/core/controller/WikiController.scala
+++ b/src/main/scala/gitbucket/core/controller/WikiController.scala
@@ -10,7 +10,7 @@
 import gitbucket.core.util.SyntaxSugars._
 import gitbucket.core.util.Implicits._
 import gitbucket.core.util.Directory._
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.eclipse.jgit.api.Git
 import org.scalatra.i18n.Messages
 
@@ -226,8 +226,8 @@
   })
 
   private def unique: Constraint = new Constraint(){
-    override def validate(name: String, value: String, params: Map[String, String], messages: Messages): Option[String] =
-      getWikiPageList(params("owner"), params("repository")).find(_ == value).map(_ => "Page already exists.")
+    override def validate(name: String, value: String, params: Map[String, Seq[String]], messages: Messages): Option[String] =
+      getWikiPageList(params("owner").head, params("repository").head).find(_ == value).map(_ => "Page already exists.")
   }
 
   private def pagename: Constraint = new Constraint(){
diff --git a/src/main/scala/gitbucket/core/util/Validations.scala b/src/main/scala/gitbucket/core/util/Validations.scala
index 6cd693c..be580d7 100644
--- a/src/main/scala/gitbucket/core/util/Validations.scala
+++ b/src/main/scala/gitbucket/core/util/Validations.scala
@@ -1,6 +1,6 @@
 package gitbucket.core.util
 
-import io.github.gitbucket.scalatra.forms._
+import org.scalatra.forms._
 import org.scalatra.i18n.Messages
 
 trait Validations {