diff --git a/src/storage.cr b/src/storage.cr
index e2a42a0..54e5638 100644
--- a/src/storage.cr
+++ b/src/storage.cr
@@ -70,7 +70,7 @@ class DNSManager::Storage
 
 		# Verify if the domain is acceptable.
 		matching_domains = accepted_domains.select { |adomain| domain.ends_with? adomain }
-		unless matching_domains
+		unless matching_domains.size > 0
 			Baguette::Log.warning "trying to add an unacceptable domain: #{domain}"
 			return Response::UnacceptableDomain.new
 		end