diff --git a/rsconnect/bundle.py b/rsconnect/bundle.py
index b9783c40..3f60205a 100644
--- a/rsconnect/bundle.py
+++ b/rsconnect/bundle.py
@@ -670,8 +670,7 @@ def create_file_list(
     excludes = excludes if excludes else []
     glob_set = create_glob_set(path, excludes)
     exclude_paths = {Path(p) for p in excludes}
-    file_set = set()  # type: typing.Set[str]
-    file_set.union(extra_files)
+    file_set = set(extra_files)  # type: typing.Set[str]
 
     if isfile(path):
         file_set.add(path)