diff --git a/lib/customer_usage.rb b/lib/customer_usage.rb
index 2a6dd0c6e016e617a4ed4d16de38e25cd28e7c69..4d206cf2a6337da091434ba0eed7452e306d4398 100644
--- a/lib/customer_usage.rb
+++ b/lib/customer_usage.rb
@@ -29,7 +29,7 @@ class CustomerUsage
 	end
 
 	def incr_message_usage(recipients:, body: nil)
-		amount = recipients.each_slice(10).count
+		amount = [recipients.each_slice(10).count, 1].max
 		today = Time.now.utc.to_date
 		EMPromise.all([
 			expire_message_usage,