diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 58482db55..6f7381486 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -928,6 +928,10 @@ class ChoiceField(Field):
         ])
 
         super(ChoiceField, self).__init__(**kwargs)
+        
+        if not self.required:
+            self.choices[''] = ''
+            self.choice_strings_to_values[''] = ''
 
     def to_internal_value(self, data):
         try: