diff --git a/rest_framework/test.py b/rest_framework/test.py
index 690303fbf..a919f989d 100644
--- a/rest_framework/test.py
+++ b/rest_framework/test.py
@@ -150,6 +150,8 @@ class APIRequestFactory(DjangoRequestFactory):
         """
         Encode the data returning a two tuple of (bytes, content_type)
         """
+        if data is None:
+            return (b'', content_type)
 
         assert format is None or content_type is None, (
             'You may not set both `format` and `content_type`.'
@@ -161,9 +163,6 @@ class APIRequestFactory(DjangoRequestFactory):
             except AttributeError:
                 pass
 
-            if data is None:
-                data = ''
-
             # Content type specified explicitly, treat data as a raw bytestring
             ret = force_bytes(data, settings.DEFAULT_CHARSET)
 
@@ -181,6 +180,7 @@ class APIRequestFactory(DjangoRequestFactory):
 
             # Use format and render the data into a bytestring
             renderer = self.renderer_classes[format]()
+            ret = renderer.render(data)
 
             # Determine the content-type header from the renderer
             content_type = renderer.media_type
@@ -189,14 +189,9 @@ class APIRequestFactory(DjangoRequestFactory):
                     content_type, renderer.charset
                 )
 
-            if data is None:
-                ret = ''
-            else:
-                ret = renderer.render(data)
-
-            # Coerce text to bytes if required.
-            if isinstance(ret, str) and renderer.charset:
-                ret = ret.encode(renderer.charset)
+                # Coerce text to bytes if required.
+                if isinstance(ret, str):
+                    ret = ret.encode(renderer.charset)
 
         return ret, content_type