diff --git a/rest_framework/utils/serializer_helpers.py b/rest_framework/utils/serializer_helpers.py
index ddf160868..d113881f1 100644
--- a/rest_framework/utils/serializer_helpers.py
+++ b/rest_framework/utils/serializer_helpers.py
@@ -108,11 +108,12 @@ class NestedBoundField(BoundField):
 
     def as_form_field(self):
         values = {}
-        for key, value in self.value.items():
-            if isinstance(value, (list, dict)):
-                values[key] = value
-            else:
-                values[key] = '' if value is None else force_text(value)
+        if self.value:
+            for key, value in self.value.items():
+                if isinstance(value, (list, dict)):
+                    values[key] = value
+                else:
+                    values[key] = '' if value is None else force_text(value)
         return self.__class__(self._field, values, self.errors, self._prefix)