diff --git a/.gitignore b/.gitignore
index 72364f9..9e00340 100644
--- a/.gitignore
+++ b/.gitignore
@@ -87,3 +87,6 @@ ENV/
 
 # Rope project settings
 .ropeproject
+
+# PyCharm project settings
+.idea/
diff --git a/bunyan/formatter.py b/bunyan/formatter.py
index 6cbf391..5142f52 100644
--- a/bunyan/formatter.py
+++ b/bunyan/formatter.py
@@ -4,7 +4,7 @@
 Provides logging compatibility with Bunyan standard and enceforth CLI.
 """
 import datetime
-import json
+import simplejson as json
 import logging
 import re
 import socket
@@ -16,6 +16,7 @@
 try:
   from collections import OrderedDict
 except ImportError:
+  OrderedDict = dict
   pass
 
 def object_startswith(key, value):
@@ -127,7 +128,7 @@ def jsonify_log_record(self, log_record):
     """
     Returns a json string of the log record.
     """
-    return json.dumps(log_record, default = self.json_default)
+    return json.dumps(log_record, default = self.json_default, ignore_nan=True)
 
   def format(self, record):
     """
@@ -137,7 +138,12 @@ def format(self, record):
 
     if isinstance(record.msg, dict):
       message_dict = record.msg
-      record.message = None
+      if len(record.args) == 1 and isinstance(record.args[0], str):
+        # bunyan style log method: fields object + msg string
+        record.msg = record.args[0]
+        record.message = record.args[0] % message_dict
+      else:
+        record.message = None
     else:
       record.message = record.getMessage()
     # only format time if needed
@@ -149,10 +155,7 @@ def format(self, record):
     if record.exc_info and not message_dict.get('exc_info'):
       message_dict['exc_info'] = self.formatException(record.exc_info)
 
-    try:
-      log_record = OrderedDict()
-    except NameError:
-      log_record = {}
+    log_record = OrderedDict()
 
     self.add_fields(log_record, record, message_dict)
     log_record = self.process_log_record(log_record)
diff --git a/requirements.txt b/requirements.txt
index e69de29..322630e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -0,0 +1 @@
+simplejson