diff --git a/test/command_line/helper/groonga_log.rb b/test/command_line/helper/groonga_log.rb
index 609397fa84..f21b8b62b3 100644
--- a/test/command_line/helper/groonga_log.rb
+++ b/test/command_line/helper/groonga_log.rb
@@ -232,7 +232,7 @@ def groonga_log_content
   end
 
   def normalized_groonga_log_content
-    normalize_groonga_log(groonga_log_content).encode("locale")
+    normalize_groonga_log(groonga_log_content)
   end
 
   private