diff --git a/app/models/prometheus_metric.rb b/app/models/prometheus_metric.rb
index 9527c596088..dbb0fd19b74 100644
--- a/app/models/prometheus_metric.rb
+++ b/app/models/prometheus_metric.rb
@@ -23,7 +23,8 @@ class PrometheusMetric < ActiveRecord::Base
   validates :y_label, presence: true
   validates :unit, presence: true
 
-  validate :require_project
+  validates :project, presence: true, unless: :common?
+  validates :project, absence: true, if: :common?
 
   scope :common, -> { where(common: true) }
 
@@ -85,14 +86,4 @@ class PrometheusMetric < ActiveRecord::Base
       }
     end
   end
-
-  private
-
-  def require_project
-    if project
-      errors.add(:project, "cannot be set if this is common metric") if common?
-    else
-      errors.add(:project, "has to be set when this is project-specific metric") unless common?
-    end
-  end
 end