diff --git a/rest_framework/utils/field_mapping.py b/rest_framework/utils/field_mapping.py
index b16e9df08..b2f4dd80e 100644
--- a/rest_framework/utils/field_mapping.py
+++ b/rest_framework/utils/field_mapping.py
@@ -106,7 +106,7 @@ def get_field_kwargs(field_name, model_field):
     # Ensure that max_length is passed explicitly as a keyword arg,
     # rather than as a validator.
     max_length = getattr(model_field, 'max_length', None)
-    if max_length is not None:
+    if max_length is not None and isinstance(model_field, models.CharField):
         kwargs['max_length'] = max_length
         validator_kwarg = [
             validator for validator in validator_kwarg