don't optimize empty strings
diff --git a/Lib/plat-mac/plistlib.py b/Lib/plat-mac/plistlib.py
index 1556d5f..5f2c47f 100644
--- a/Lib/plat-mac/plistlib.py
+++ b/Lib/plat-mac/plistlib.py
@@ -88,7 +88,7 @@
         self.writeln("</%s>" % element)
 
     def simpleElement(self, element, value=None):
-        if value:
+        if value is not None:
             value = _encode(value)
             self.writeln("<%s>%s</%s>" % (element, value, element))
         else: