diff --git a/app/models/foreman_tasks/triggering.rb b/app/models/foreman_tasks/triggering.rb
index 6009e5384..d506cf95d 100644
--- a/app/models/foreman_tasks/triggering.rb
+++ b/app/models/foreman_tasks/triggering.rb
@@ -38,6 +38,7 @@ class Triggering < ApplicationRecord
                                :if => proc { |t| t.recurring? && t.input_type == :monthly } }
     validate :can_start_recurring, :if => :recurring?
     validate :can_start_future, :if => :future?
+    validate :start_at_is_not_past
 
     def self.new_from_params(params = {})
       new(params.except(:mode, :start_at, :start_before)).tap do |triggering|
@@ -121,5 +122,9 @@ def can_start_future
       parse_start_at!
       errors.add(:start_before_raw, _('The task could not be started')) if !start_before.nil? && start_before < start_at
     end
+
+    def start_at_is_not_past
+      errors.add(:start_at, _('is in the past')) if !start_at.nil? && Time.zone.parse(start_at_raw) < Time.zone.now
+    end
   end
 end
diff --git a/test/unit/triggering_test.rb b/test/unit/triggering_test.rb
index 6e511b4b1..6d867d6f7 100644
--- a/test/unit/triggering_test.rb
+++ b/test/unit/triggering_test.rb
@@ -10,7 +10,7 @@ class TriggeringTest < ActiveSupport::TestCase
       triggering = FactoryBot.build(:triggering, :future)
       assert_predicate(triggering, :valid?)
       triggering.start_before = triggering.start_at - 120
-      assert_not_predicate(triggering, :valid?)
+      assert_not_predicate(triggering, :valid?).returns(false)
     end
 
     it 'is invalid when recurring logic is invalid' do