diff --git a/util/format.py b/util/format.py
index 1299778..43c58c9 100644
--- a/util/format.py
+++ b/util/format.py
@@ -50,9 +50,12 @@ def formatDate(dt=None, type='date', variant='medium', lang='de'):
     return fmt.format(dt or datetime.now())
 
 
-def formatNumber(num, type='decimal', lang='de', pattern=u'#,##0.00;-#,##0.00'):
+def formatNumber(num, type='decimal', lang='de', 
+                 pattern=u'#,##0.00;-#,##0.00', precision=2):
     loc = locales.getLocale(lang)
     fmt = loc.numbers.getFormatter(type)
+    if precision:
+        num = round(num, precision)     # avoid zope.i18n formatting bug
     return fmt.format(num, pattern=pattern)
 
 
diff --git a/util/format.txt b/util/format.txt
index b96450a..cfab90f 100644
--- a/util/format.txt
+++ b/util/format.txt
@@ -15,3 +15,5 @@ Basic Formatting Functions
 
   >>> format.formatNumber(17.2)
   u'17,20'
+  >>> format.formatNumber(13399.99999997)
+  u'13.400,00'