diff --git a/reviewboard/diffviewer/diffutils.py b/reviewboard/diffviewer/diffutils.py
index 6692c034cb7dbcdcbf3603b8d8b3eddd7051bf49..45c03aa571f4fb8c0fc7960097b7e59ea05a3e1f 100644
--- a/reviewboard/diffviewer/diffutils.py
+++ b/reviewboard/diffviewer/diffutils.py
@@ -600,13 +600,13 @@ def get_diff_files(diffset, filediff=None, interdiffset=None,
             else:
                 filediffs = diffset.files.select_related().all()
 
-            filediffs = list(filediffs)
-
             filediffs = exclude_filediff_ancestors(filediffs, diffset,
                                                    diffset_file_graph)
         else:
             filediffs = diffset.files.select_related().all()
 
+        filediffs = list(filediffs)
+
         if interdiffset:
             log_timer = log_timed("Generating diff file info for "
                                   "interdiffset ids %s-%s" %