diff --git a/json_field/forms.py b/json_field/forms.py
index d092958..5991cf6 100644
--- a/json_field/forms.py
+++ b/json_field/forms.py
@@ -11,6 +11,7 @@ class JSONFormField(fields.Field):
 
     def __init__(self, *args, **kwargs):
         from .fields import JSONEncoder, JSONDecoder
+        kwargs.pop('max_length', None)
         self.evaluate = kwargs.pop('evaluate', False)
         self.encoder_kwargs = kwargs.pop('encoder_kwargs', {'cls':JSONEncoder})
         self.decoder_kwargs = kwargs.pop('decoder_kwargs', {'cls':JSONDecoder, 'parse_float':Decimal})