diff --git a/repo2docker/buildpacks/base.py b/repo2docker/buildpacks/base.py
index 06f52224..f8dcf758 100644
--- a/repo2docker/buildpacks/base.py
+++ b/repo2docker/buildpacks/base.py
@@ -612,6 +612,7 @@ def _filter_tar(tarinfo):
         exclude = []
 
         for ignore_file_name in [".dockerignore", ".containerignore"]:
+            ignore_file_name = self.binder_path(ignore_file_name)
             if os.path.exists(ignore_file_name):
                 with open(ignore_file_name) as ignore_file:
                     cleaned_lines = [