diff --git a/bibtex-compatibility.py b/bibtex-compatibility.py
index da86f6a4..d4054b49 100755
--- a/bibtex-compatibility.py
+++ b/bibtex-compatibility.py
@@ -33,7 +33,7 @@
 date_re = re.compile(r"date.*{(\d+)-?(\d+)?.*}")
 
 for line in old_db:
-    date_pattern = date_re.search(line)
+    date_pattern = date_re.search(line) if "date" in line else None
     if date_pattern:
         new_db.write("  year = {{{0:s}}},\n".format(date_pattern.group(1)))
         # print "  year = {{{0:s}}},\n".format(date_pattern.group(1)),