diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index f975c45e..71ec0afb 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -31,8 +31,9 @@ class Exercise < ApplicationRecord
 
   validate :valid_main_file?
   validates :description, presence: true
-  # validates :execution_environment_id, presence: true # TODO make this conditional - but based on what?
+  validates :execution_environment_id, presence: true, if: -> { !unpublished? } # TODO make this conditional - but based on what?
   validates :public, boolean_presence: true
+  validates :unpublished, boolean_presence: true
   validates :title, presence: true
   validates :token, presence: true, uniqueness: true
   validates_uniqueness_of :uuid