diff --git a/lib/features/support/interface/traces_interface.rb b/lib/features/support/interface/traces_interface.rb
index 60f4e331..87a16e33 100644
--- a/lib/features/support/interface/traces_interface.rb
+++ b/lib/features/support/interface/traces_interface.rb
@@ -94,7 +94,7 @@ def assert_field_attribute_one_of(field, attribute, attr_type, values)
   Maze.check.include(found_attribute['value'], attr_type, "Payload field '#{field}' attribute '#{attribute}' value was not an '#{attr_type}', found '#{found_attribute['value']}'")
 
   attribute_value = found_attribute['value'][attr_type]
-  allowable_values = values.raw
+  allowable_values = values.raw.flatten
   failure_message = "The payload field '#{field}' attribute '#{attribute}' (#{attribute_value}) was not one of: '#{allowable_values}'"
   Maze.check.include(allowable_values, attribute_value, failure_message)
 end