diff --git a/lib/unicorn/unicorn_json_log_formatter.rb b/lib/unicorn/unicorn_json_log_formatter.rb
index 7d68d7368e..d0695d999a 100644
--- a/lib/unicorn/unicorn_json_log_formatter.rb
+++ b/lib/unicorn/unicorn_json_log_formatter.rb
@@ -4,7 +4,7 @@ class UnicornJSONLogFormatter < Logger::Formatter
   def call(severity, datetime, progname, message)
     default = {
       severity: severity,
-      datetime: datetime,
+      datetime: DateTime.parse(datetime).to_s,
       progname: progname || '',
       pid: $$,
     }