diff --git a/devops-service/db/validators/helpers/run_list.rb b/devops-service/db/validators/helpers/run_list.rb
index 3fa9418..e1fe807 100644
--- a/devops-service/db/validators/helpers/run_list.rb
+++ b/devops-service/db/validators/helpers/run_list.rb
@@ -10,7 +10,7 @@ module Validators
 
     def message
       invalid_elements_as_string = @invalid_elements.join("', '")
-      "Invalid run list elements: '#{invalid_elements_as_string}'. Each element should be role or recipe."
+      "Invalid run list elements: '#{invalid_elements_as_string}'. Each element should be a role or a recipe."
     end
   end
 end
diff --git a/devops-service/tests/templates/api_v2/10_create/40_deploy_env.feature.erb b/devops-service/tests/templates/api_v2/10_create/40_deploy_env.feature.erb
index a8cafc6..91f0d59 100644
--- a/devops-service/tests/templates/api_v2/10_create/40_deploy_env.feature.erb
+++ b/devops-service/tests/templates/api_v2/10_create/40_deploy_env.feature.erb
@@ -20,7 +20,7 @@ Feature: Create deploy env
     }
     """
     Then response should be '400'
-    And response error should be "Invalid run list elements: 'wrong_role'. Each element should be role or recipe."
+    And response error should be "Invalid run list elements: 'wrong_role'. Each element should be a role or a recipe."
 
   @openstack
   Scenario: Send deploy env with invalid expiration for project <%= openstack_project_name %>
@@ -162,7 +162,7 @@ Feature: Create deploy env
     }
     """
     Then response should be '400'
-    And response error should be "Invalid run list elements: 'wrong_role'. Each element should be role or recipe."
+    And response error should be "Invalid run list elements: 'wrong_role'. Each element should be a role or a recipe."
 
   @ec2
   Scenario: Send deploy env with invalid expiration for project <%= ec2_project_name %>
@@ -288,7 +288,7 @@ Feature: Create deploy env
     }
     """
     Then response should be '400'
-    And response error should be "Invalid run list elements: 'wrong_role'. Each element should be role or recipe."
+    And response error should be "Invalid run list elements: 'wrong_role'. Each element should be a role or a recipe."
 
   @static
   Scenario: Send deploy env with invalid expiration for project <%= static_project_name %>