diff --git a/lib/logger/formatter.rb b/lib/logger/formatter.rb
index 62bff70..34e07bc 100644
--- a/lib/logger/formatter.rb
+++ b/lib/logger/formatter.rb
@@ -13,7 +13,7 @@ def initialize
     end
 
     def call(severity, time, progname, msg)
-      Format % [severity[0..0], format_datetime(time), Process.pid, severity, progname,
+      Format % [severity[0, 1], format_datetime(time), Process.pid, severity, progname,
         msg2str(msg)]
     end