diff --git a/backend/internal/service/openai_gateway_record_usage_test.go b/backend/internal/service/openai_gateway_record_usage_test.go
index 421f3fec..6fd94a3e 100644
--- a/backend/internal/service/openai_gateway_record_usage_test.go
+++ b/backend/internal/service/openai_gateway_record_usage_test.go
@@ -44,12 +44,10 @@ type openAIRecordUsageSubRepoStub struct {
 
 	incrementCalls int
 	incrementErr   error
-	lastAmount     float64
 }
 
 func (s *openAIRecordUsageSubRepoStub) IncrementUsage(ctx context.Context, id int64, costUSD float64) error {
 	s.incrementCalls++
-	s.lastAmount = costUSD
 	return s.incrementErr
 }