diff --git a/app/models/execution_environment.rb b/app/models/execution_environment.rb
index d4138000..3ca6da6c 100644
--- a/app/models/execution_environment.rb
+++ b/app/models/execution_environment.rb
@@ -16,7 +16,7 @@ class ExecutionEnvironment < ApplicationRecord
   has_many :exercises
   belongs_to :file_type
   has_many :error_templates
-  belongs_to :testrun_execution_environment, optional: true, dependent: :destroy
+  has_many :testrun_execution_environments, dependent: :destroy
 
   scope :with_exercises, -> { where('id IN (SELECT execution_environment_id FROM exercises)') }