diff --git a/config/initializers/metrics.rb b/config/initializers/metrics.rb
index 5b0f4f1..a50a8b1 100644
--- a/config/initializers/metrics.rb
+++ b/config/initializers/metrics.rb
@@ -26,12 +26,15 @@
     end
     gauge :total_stacks do
       comment 'The total number of stacks.'
+      aggregation :sum
     end
     gauge :total_healthy_stacks do
       comment 'The total number of healthy stacks.'
+      aggregation :sum
     end
     gauge :total_unhealthy_stacks do
       comment 'The total number of unhealthy stacks.'
+      aggregation :sum
     end
 
     collect do