--- /usr/lib/python2.3/cgitb.py	2004-10-01 12:26:42.000000000 +0100
+++ cgitb.py	2005-01-28 17:34:40.000000000 +0000
@@ -115,7 +115,8 @@
 
         rows = ['<tr><td bgcolor="#d8bbff">%s%s %s</td></tr>' %
                 ('<big>&nbsp;</big>', link, call)]
-        if index is not None:
+
+        if index is not None and len(lines) > 0:
             i = lnum - index
             for line in lines:
                 num = small('&nbsp;' * (5-len(str(i))) + str(i)) + '&nbsp;'
@@ -125,6 +126,10 @@
                 else:
                     rows.append('<tr><td>%s</td></tr>' % grey(line))
                 i += 1
+        else:
+            num = small('&nbsp;' * (5-len(str(lnum))) + str(lnum)) + '&nbsp;'
+            line = '<tt>%s%s</tt>' % (num, pydoc.html.preformat('Source unavailable'))
+            rows.append('<tr><td bgcolor="#ffccee">%s</td></tr>' % line)
 
         done, dump = {}, []
         for name, where, value in vars: