diff --git a/Tools/c-analyzer/c_analyzer/common/files.py b/Tools/c-analyzer/c_analyzer/common/files.py
index f630afe..a8a0447 100644
--- a/Tools/c-analyzer/c_analyzer/common/files.py
+++ b/Tools/c-analyzer/c_analyzer/common/files.py
@@ -60,7 +60,7 @@
 
 
 def iter_files(root, suffix=None, relparent=None, *,
-               get_files=os.walk,
+               get_files=None,
                _glob=glob_tree,
                _walk=walk_tree,
                ):
@@ -75,6 +75,8 @@
     if "relparent" is provided then it is used to resolve each
     filename as a relative path.
     """
+    if get_files is None:
+        get_files = os.walk
     if not isinstance(root, str):
         roots = root
         for root in roots: