diff --git a/src/bagit/__init__.py b/src/bagit/__init__.py
index c17b1f2..890dbd8 100755
--- a/src/bagit/__init__.py
+++ b/src/bagit/__init__.py
@@ -133,7 +133,7 @@ def find_locale_dir():
 
 #: Convenience function used everywhere we want to open a file to read text
 #: rather than undecoded bytes:
-open_text_file = partial(codecs.open, encoding="utf-8", errors="strict")
+open_text_file = partial(open, encoding="utf-8", errors="strict")
 
 # This is the same as decoding the byte values in codecs.BOM:
 UNICODE_BYTE_ORDER_MARK = "\ufeff"
@@ -1423,8 +1423,8 @@ def _encode_filename(s):
 
 
 def _decode_filename(s):
-    s = re.sub(r"%0D", "\r", s, re.IGNORECASE)
-    s = re.sub(r"%0A", "\n", s, re.IGNORECASE)
+    s = re.sub(r"%0D", "\r", s, flags=re.IGNORECASE)
+    s = re.sub(r"%0A", "\n", s, flags=re.IGNORECASE)
     return s