diff --git a/lib/classifier-reborn/backends/bayes_redis_backend.rb b/lib/classifier-reborn/backends/bayes_redis_backend.rb
index db95772..7aba1a9 100644
--- a/lib/classifier-reborn/backends/bayes_redis_backend.rb
+++ b/lib/classifier-reborn/backends/bayes_redis_backend.rb
@@ -77,7 +77,7 @@ def update_category_word_count(category, diff)
     end
 
     def add_category(category)
-      @redis.sadd(:category_keys, category)
+      @redis.sadd?(:category_keys, category)
     end
 
     def category_keys