diff --git a/spec/lib/solidus_subscriptions/subscription_generator_spec.rb b/spec/lib/solidus_subscriptions/subscription_generator_spec.rb
index 13699884..02ed05e2 100644
--- a/spec/lib/solidus_subscriptions/subscription_generator_spec.rb
+++ b/spec/lib/solidus_subscriptions/subscription_generator_spec.rb
@@ -75,7 +75,7 @@
         weekly_subscriptions,
         expiring_subscriptions,
       ]
-      grouping_result = described_class.group(subscriptions.sum)
+      grouping_result = described_class.group(subscriptions.flatten)
 
       expect(grouping_result).to match_array(subscriptions)
     end