diff --git a/abcfirstline.py b/abcfirstline.py
index 26a5daa..ab6ccb0 100755
--- a/abcfirstline.py
+++ b/abcfirstline.py
@@ -11,7 +11,7 @@ def process(inf):
     for line in inf:
         line = line.strip()
         start = line[:2]
-        if start[0] != "|" and start[1] == ":":
+        if len(start) > 1 and start[0] != "|" and start[1] == ":":
             if start[0] in ["M", "K", "L"]:
                 print line
         elif start[0] != "%":