diff --git a/spec/filters/unique.rb b/spec/filters/unique.rb
index 63531d659..6d9d42f9d 100644
--- a/spec/filters/unique.rb
+++ b/spec/filters/unique.rb
@@ -8,7 +8,7 @@ describe LogStash::Filters::Unique do
     config <<-CONFIG
     filter {
       unique {
-        fields => ["noisy_field"]
+        fields => ["noisy_field", "not_an_array"]
       }
     }
     CONFIG