diff --git a/app/assets/javascripts/app/controllers/_ui_element/_application_selector.coffee b/app/assets/javascripts/app/controllers/_ui_element/_application_selector.coffee
index e0b6d95e6..7e12a836c 100644
--- a/app/assets/javascripts/app/controllers/_ui_element/_application_selector.coffee
+++ b/app/assets/javascripts/app/controllers/_ui_element/_application_selector.coffee
@@ -113,7 +113,7 @@ class App.UiElement.ApplicationSelector
                 config.operator = operator
               elements["#{groupKey}.#{config.name}"] = config
 
-            if config.tag == 'select'
+            if /^(tree_|multi)?select$/.test(config.tag)
               config.multiple = true
 
     if attribute.out_of_office
diff --git a/app/assets/javascripts/app/controllers/_ui_element/core_workflow_perform.coffee b/app/assets/javascripts/app/controllers/_ui_element/core_workflow_perform.coffee
index 53c048aeb..c22917f07 100644
--- a/app/assets/javascripts/app/controllers/_ui_element/core_workflow_perform.coffee
+++ b/app/assets/javascripts/app/controllers/_ui_element/core_workflow_perform.coffee
@@ -73,7 +73,7 @@ class App.UiElement.core_workflow_perform extends App.UiElement.ApplicationSelec
           config = _.clone(row)
           if config.tag is 'boolean'
             config.tag = 'select'
-          if /^((multi)?select)$/.test(config.tag)
+          if /^(tree_|multi)?select$/.test(config.tag)
             config.multiple = true
             config.default  = undefined
           if config.type is 'email' || config.type is 'tel'
@@ -121,14 +121,14 @@ class App.UiElement.core_workflow_perform extends App.UiElement.ApplicationSelec
     currentOperator = elementRow.find('.js-operator option:selected').attr('value')
     name            = @buildValueName(elementFull, elementRow, groupAndAttribute, elements, meta, attribute)
 
-    if !_.contains(['add_option', 'remove_option', 'set_fixed_to', 'select', 'multiselect', 'execute', 'fill_in', 'fill_in_empty'], currentOperator)
+    if !_.contains(['add_option', 'remove_option', 'set_fixed_to', 'select', 'execute', 'fill_in', 'fill_in_empty'], currentOperator)
       elementRow.find('.js-value').addClass('hide').html('<input type="hidden" name="' + name + '" value="true" />')
       return
 
     super(elementFull, elementRow, groupAndAttribute, elements, meta, attribute)
 
   @buildValueConfigMultiple: (config, meta) ->
-    if _.contains(['add_option', 'remove_option', 'set_fixed_to', 'select', 'multiselect'], meta.operator)
+    if _.contains(['add_option', 'remove_option', 'set_fixed_to', 'select'], meta.operator)
       config.multiple = true
       config.nulloption = true
     else
diff --git a/app/assets/javascripts/app/controllers/_ui_element/multiselect_search.coffee b/app/assets/javascripts/app/controllers/_ui_element/multiselect_search.coffee
new file mode 100644
index 000000000..02aefad66
--- /dev/null
+++ b/app/assets/javascripts/app/controllers/_ui_element/multiselect_search.coffee
@@ -0,0 +1,35 @@
+# coffeelint: disable=camel_case_classes
+class App.UiElement.multiselect_search extends App.UiElement.ApplicationUiElement
+  @render: (attribute, params) ->
+
+    # set multiple option
+    if attribute.multiple
+      attribute.multiple = 'multiple'
+    else
+      attribute.multiple = ''
+
+    delete attribute.filter
+
+    # build options list based on config
+    @getConfigOptionList(attribute, params)
+
+    # build options list based on relation
+    @getRelationOptionList(attribute, params)
+
+    # add null selection if needed
+    @addNullOption(attribute, params)
+
+    # sort attribute.options
+    @sortOptions(attribute, params)
+
+    # find selected/checked item of list
+    @selectedOptions(attribute, params)
+
+    # disable item of list
+    @disabledOptions(attribute, params)
+
+    # filter attributes
+    @filterOption(attribute, params)
+
+    # return item
+    $( App.view('generic/select')(attribute: attribute) )
diff --git a/app/assets/javascripts/app/controllers/_ui_element/ticket_perform_action.coffee b/app/assets/javascripts/app/controllers/_ui_element/ticket_perform_action.coffee
index 93f185047..1b8cfb7fc 100644
--- a/app/assets/javascripts/app/controllers/_ui_element/ticket_perform_action.coffee
+++ b/app/assets/javascripts/app/controllers/_ui_element/ticket_perform_action.coffee
@@ -319,6 +319,8 @@ class App.UiElement.ticket_perform_action
         config['value'] = _.clone(attribute.value[groupAndAttribute]['value'])
       config.multiple = false
       config.nulloption = config.null
+      if config.tag is 'multiselect'
+        config.multiple = true
       if config.tag is 'checkbox'
         config.tag = 'select'
       tagSearch = "#{config.tag}_search"
diff --git a/app/assets/javascripts/app/controllers/_ui_element/tree_select_search.coffee b/app/assets/javascripts/app/controllers/_ui_element/tree_select_search.coffee
index 7022ad61d..ff35e0274 100644
--- a/app/assets/javascripts/app/controllers/_ui_element/tree_select_search.coffee
+++ b/app/assets/javascripts/app/controllers/_ui_element/tree_select_search.coffee
@@ -6,7 +6,13 @@ class App.UiElement.tree_select_search extends App.UiElement.ApplicationUiElemen
     attribute = clone(localAttribute)
 
     # set multiple option
-    attribute.multiple = 'multiple'
+    if attribute.multiple
+      attribute.multiple = 'multiple'
+    else
+      attribute.multiple = ''
+
+    # add null selection if needed
+    @addNullOption(attribute, params)
 
     # sort attribute.options
     @sortOptions(attribute, params)
diff --git a/app/assets/javascripts/app/controllers/ticket_zoom/form_handler_core_workflow.coffee b/app/assets/javascripts/app/controllers/ticket_zoom/form_handler_core_workflow.coffee
index 6dbcbb007..ca3b83302 100644
--- a/app/assets/javascripts/app/controllers/ticket_zoom/form_handler_core_workflow.coffee
+++ b/app/assets/javascripts/app/controllers/ticket_zoom/form_handler_core_workflow.coffee
@@ -191,7 +191,11 @@ class App.FormHandlerCoreWorkflow
     return if _.isEmpty(data)
 
     for field, values of data
-      form.find('[name="' + field + '"]').val(data[field])
+      fieldElement = $("div[data-attribute-name='" + field + "']")
+      if fieldElement.hasClass('tree_select')
+        fieldElement.find(".js-option[data-value='" + data[field] + "']").trigger('click')
+      else
+        form.find('[name="' + field + '"]').val(data[field])
       coreWorkflowParams[classname][field] = data[field]
 
   # fill in data in input fields
diff --git a/public/assets/tests/qunit/form.js b/public/assets/tests/qunit/form.js
index a84d83478..03821c2d3 100644
--- a/public/assets/tests/qunit/form.js
+++ b/public/assets/tests/qunit/form.js
@@ -1631,3 +1631,23 @@ QUnit.test("Fixes #3909 - Wrong size for textareas in triggers and core workflow
   })
   .finally(done)
 });
+
+QUnit.test("Fixes #4024 - Tree select value cannot be set to \"-\" (empty) with Trigger/Scheduler/Core workflow.", assert => {
+  $('#qunit').append('<hr><h1>Fixes #4024 - Tree select value cannot be set to "-" (empty) with Trigger/Scheduler/Core workflow.</h1><form id="form22"></form>')
+  var el = $('#form22')
+  new App.ControllerForm({
+    el:        el,
+    model:     {
+      configure_attributes: [
+        { name: '4042_select', display: '4042_select', tag: 'select_search', null: true, nulloption: true, multiple: true, options: { 'a': 'a', 'b': 'b' } },
+        { name: '4042_multiselect', display: '4042_multiselect', tag: 'multiselect_search', null: true, nulloption: true, multiple: true, options: { 'a': 'a', 'b': 'b' } },
+        { name: '4042_tree_select', display: '4042_tree_select', tag: 'tree_select_search', null: true, nulloption: true, multiple: true, options: [{ 'value': 'a', 'name': 'a'}, { 'value': 'b', 'name': 'b'}] },
+      ],
+    },
+    autofocus: true
+  });
+
+  assert.equal(el.find('select[name="4042_select"] option[value=""]').text(), '-', '4042_select has nulloption')
+  assert.equal(el.find('select[name="4042_multiselect"] option[value=""]').text(), '-', '4042_multiselect has nulloption')
+  assert.equal(el.find('select[name="4042_tree_select"] option[value=""]').text(), '-', '4042_tree_select has nulloption')
+});
diff --git a/public/assets/tests/qunit/form_tree_select.js b/public/assets/tests/qunit/form_tree_select.js
index 92f709076..441c12ef5 100644
--- a/public/assets/tests/qunit/form_tree_select.js
+++ b/public/assets/tests/qunit/form_tree_select.js
@@ -203,6 +203,7 @@ QUnit.test("form elements check", assert => {
           "tag": "tree_select_search",
           "null": true,
           "translate": true,
+          "multiple": true,
           "value": ['aa::aab', 'bb', 'aa::aac::33'],
           "options": [
             {
diff --git a/spec/system/ticket/create_spec.rb b/spec/system/ticket/create_spec.rb
index b826787eb..004fe7d06 100644
--- a/spec/system/ticket/create_spec.rb
+++ b/spec/system/ticket/create_spec.rb
@@ -908,4 +908,42 @@ RSpec.describe 'Ticket Create', type: :system do
       expect(page).to have_no_text('Test Other Agent')
     end
   end
+
+  describe 'Tree select value cannot be set to "-" (empty) with Trigger/Scheduler/Core workflow #4024', authenticated_as: :authenticate, db_strategy: :reset do
+    let(:field_name) { SecureRandom.uuid }
+    let(:field) do
+      create :object_manager_attribute_tree_select, name: field_name, display: field_name, screens: attributes_for(:required_screen)
+      ObjectManager::Attribute.migration_execute
+    end
+    let(:workflow) do
+      create(:core_workflow,
+             object:             'Ticket',
+             condition_selected: { 'ticket.priority_id'=>{ 'operator' => 'is', 'value' => Ticket::Priority.find_by(name: '3 high').id.to_s } },
+             perform:            { "ticket.#{field_name}" => { 'operator' => 'select', 'select' => 'Incident' } })
+    end
+    let(:workflow2) do
+      create(:core_workflow,
+             object:             'Ticket',
+             condition_selected: { 'ticket.priority_id'=>{ 'operator' => 'is', 'value' => Ticket::Priority.find_by(name: '2 normal').id.to_s } },
+             perform:            { "ticket.#{field_name}" => { 'operator' => 'select', 'select' => '' } })
+    end
+
+    def authenticate
+      field
+      workflow
+      workflow2
+      true
+    end
+
+    before do
+      visit 'ticket/create'
+    end
+
+    it 'does select the field value properly' do
+      page.find('[name=priority_id]').select '3 high'
+      wait.until { page.find("input[name='#{field_name}']", visible: :all).value == 'Incident' }
+      page.find('[name=priority_id]').select '2 normal'
+      wait.until { page.find("input[name='#{field_name}']", visible: :all).value == '' }
+    end
+  end
 end