Index: pyyaml/trunk/lib/yaml/resolver.py
===================================================================
--- pyyaml/trunk/lib/yaml/resolver.py	(revision 246)
+++ pyyaml/trunk/lib/yaml/resolver.py	(revision 260)
@@ -174,5 +174,6 @@
 Resolver.add_implicit_resolver(
         u'tag:yaml.org,2002:float',
-        re.compile(ur'''^(?:[-+]?(?:[0-9][0-9_]*)?\.[0-9_]*(?:[eE][-+][0-9]+)?
+        re.compile(ur'''^(?:[-+]?(?:[0-9][0-9_]*)\.[0-9_]*(?:[eE][-+][0-9]+)?
+                    |\.[0-9_]+(?:[eE][-+][0-9]+)?
                     |[-+]?[0-9][0-9_]*(?::[0-5]?[0-9])+\.[0-9_]*
                     |[-+]?\.(?:inf|Inf|INF)