diff --git a/pdfminer/utils.py b/pdfminer/utils.py
index 9700abf..a6ccabe 100644
--- a/pdfminer/utils.py
+++ b/pdfminer/utils.py
@@ -275,6 +275,8 @@ def decode_text(s):
 # enc
 def enc(x, codec='ascii'):
     """Encodes a string for SGML/XML/HTML"""
+    if isinstance(x, bytes):
+        return ''
     x = x.replace('&', '&amp;').replace('>', '&gt;').replace('<', '&lt;').replace('"', '&quot;')
     if codec:
         x = x.encode(codec, 'xmlcharrefreplace')