diff --git a/rest_framework/utils/model_meta.py b/rest_framework/utils/model_meta.py
index 8eb00e4334..77952fbf89 100644
--- a/rest_framework/utils/model_meta.py
+++ b/rest_framework/utils/model_meta.py
@@ -92,7 +92,7 @@ def _get_fields(opts):
 
 
 def _get_to_field(field):
-    return field.to_fields[0] if field.to_fields else None
+    return getattr(field, 'to_fields', None) and field.to_fields[0]
 
 
 def _get_forward_relationships(opts):