diff --git a/src/drf_yasg/openapi.py b/src/drf_yasg/openapi.py
index a88da60..17716fa 100644
--- a/src/drf_yasg/openapi.py
+++ b/src/drf_yasg/openapi.py
@@ -1,12 +1,16 @@
+import six
+
+import collections
 import logging
 import re
 from collections import OrderedDict
 
 from coreapi.compat import urlparse
 from django.urls import get_script_prefix
+from django.utils.functional import Promise
 from inflection import camelize
 
-from .utils import filter_none
+from .utils import filter_none, force_real_str
 
 logger = logging.getLogger(__name__)
 
@@ -128,13 +132,19 @@ class SwaggerDict(OrderedDict):
         if id(obj) in memo:
             return memo[id(obj)]
 
-        if isinstance(obj, dict):
+        if isinstance(obj, Promise) and hasattr(obj, '_proxy____cast'):
+            # handle __proxy__ objects from django.utils.functional.lazy
+            obj = obj._proxy____cast()
+
+        if isinstance(obj, collections.Mapping):
             result = OrderedDict()
             memo[id(obj)] = result
             for attr, val in obj.items():
                 result[attr] = SwaggerDict._as_odict(val, memo)
             return result
-        elif isinstance(obj, (list, tuple)):
+        elif isinstance(obj, six.string_types):
+            return force_real_str(obj)
+        elif isinstance(obj, collections.Iterable) and not isinstance(obj, collections.Iterator):
             return type(obj)(SwaggerDict._as_odict(elem, memo) for elem in obj)
 
         return obj
diff --git a/src/drf_yasg/renderers.py b/src/drf_yasg/renderers.py
index 0369fed..a265688 100644
--- a/src/drf_yasg/renderers.py
+++ b/src/drf_yasg/renderers.py
@@ -4,7 +4,7 @@ from django.shortcuts import resolve_url
 from django.template.loader import render_to_string
 from django.utils.functional import Promise
 from rest_framework.renderers import BaseRenderer, JSONRenderer, TemplateHTMLRenderer
-from rest_framework.utils import json
+from rest_framework.utils import encoders, json
 
 from .app_settings import redoc_settings, swagger_settings
 from .codecs import VALIDATORS, OpenAPICodecJson, OpenAPICodecYaml
@@ -76,7 +76,7 @@ class _UIRenderer(BaseRenderer):
     def set_context(self, renderer_context, swagger=None):
         renderer_context['title'] = swagger.info.title or '' if swagger else ''
         renderer_context['version'] = swagger.info.version or '' if swagger else ''
-        renderer_context['oauth2_config'] = json.dumps(self.get_oauth2_config())
+        renderer_context['oauth2_config'] = json.dumps(self.get_oauth2_config(), cls=encoders.JSONEncoder)
         renderer_context['USE_SESSION_AUTH'] = swagger_settings.USE_SESSION_AUTH
         renderer_context.update(self.get_auth_urls())
 
@@ -120,7 +120,7 @@ class SwaggerUIRenderer(_UIRenderer):
 
     def set_context(self, renderer_context, swagger=None):
         super(SwaggerUIRenderer, self).set_context(renderer_context, swagger)
-        renderer_context['swagger_settings'] = json.dumps(self.get_swagger_ui_settings())
+        renderer_context['swagger_settings'] = json.dumps(self.get_swagger_ui_settings(), cls=encoders.JSONEncoder)
 
     def get_swagger_ui_settings(self):
         data = {
@@ -157,7 +157,7 @@ class ReDocRenderer(_UIRenderer):
 
     def set_context(self, renderer_context, swagger=None):
         super(ReDocRenderer, self).set_context(renderer_context, swagger)
-        renderer_context['redoc_settings'] = json.dumps(self.get_redoc_settings())
+        renderer_context['redoc_settings'] = json.dumps(self.get_redoc_settings(), cls=encoders.JSONEncoder)
 
     def get_redoc_settings(self):
         data = {