Index: pyyaml/trunk/lib/yaml/scanner.py
===================================================================
--- pyyaml/trunk/lib/yaml/scanner.py	(revision 136)
+++ pyyaml/trunk/lib/yaml/scanner.py	(revision 138)
@@ -702,5 +702,4 @@
         # DOCUMENT-END:     ^ '...' (' '|'\n')
         if self.column == 0:
-            prefix = self.peek(4)
             if self.prefix(3) == u'...'  \
                     and self.peek(3) in u'\0 \t\r\n\x85\u2028\u2029':