Index: pyyaml/trunk/lib/yaml/emitter.py
===================================================================
--- pyyaml/trunk/lib/yaml/emitter.py	(revision 137)
+++ pyyaml/trunk/lib/yaml/emitter.py	(revision 141)
@@ -466,5 +466,5 @@
                 self.prepared_tag = None
                 return
-            if self.event.implicit[0] and not tag:
+            if self.event.implicit[0] and tag is None:
                 tag = u'!'
                 self.prepared_tag = None
@@ -473,5 +473,5 @@
                 self.prepared_tag = None
                 return
-        if not tag:
+        if tag is None:
             raise EmitterError("tag is not specified")
         if self.prepared_tag is None:
@@ -609,5 +609,5 @@
                     or ch in u'-_'):
                 raise EmitterError("invalid character %r in the anchor: %r"
-                        % (ch.encode('utf-8'), text.encode('utf-8')))
+                        % (ch.encode('utf-8'), anchor.encode('utf-8')))
         return anchor