diff --git a/setup.py b/setup.py
index 9be4c05..5a392f1 100755
--- a/setup.py
+++ b/setup.py
@@ -10,9 +10,9 @@
       classifiers=['Programming Language :: Python :: 3 :: Only'],
       url="http://singer.io",
       install_requires=[
-          'pytz==2018.4',
-          'jsonschema==2.6.0',
-          'simplejson==3.11.1',
+          'pytz>=2019.1',
+          'jsonschema>=2.6.0',
+          'simplejson>=3.16.0',
           'python-dateutil>=2.6.0',
           'backoff==1.3.2',
       ],
diff --git a/singer/messages.py b/singer/messages.py
index 0602cf5..47e3f96 100644
--- a/singer/messages.py
+++ b/singer/messages.py
@@ -209,8 +209,10 @@ def parse_message(msg):
         return None
 
 
-def format_message(message):
-    return json.dumps(message.asdict(), use_decimal=True)
+def format_message(message, **kwargs):
+    return json.dumps(message.asdict(),
+                      use_decimal=kwargs.pop('use_decimal', True),
+                      **kwargs)
 
 
 def write_message(message):