diff -ru b/csv.py c/csv.py
--- b/csv.py	2010-11-24 21:46:54.000000000 +0100
+++ c/csv.py	2010-11-24 21:50:22.000000000 +0100
@@ -176,11 +176,11 @@
 
         quotechar, doublequote, delimiter, skipinitialspace = \
                    self._guess_quote_and_delimiter(sample, delimiters)
-        if not delimiter:
+        if delimiter is None:
             delimiter, skipinitialspace = self._guess_delimiter(sample,
                                                                 delimiters)
 
-        if not delimiter:
+        if delimiter is None:
             raise Error, "Could not determine delimiter"
 
         class dialect(Dialect):