diff --git a/lib/yaml/resolver.py b/lib/yaml/resolver.py
index 3522bdaa..8fb170b2 100644
--- a/lib/yaml/resolver.py
+++ b/lib/yaml/resolver.py
@@ -176,8 +176,8 @@ class Resolver(BaseResolver):
 
 Resolver.add_implicit_resolver(
         'tag:yaml.org,2002:float',
-        re.compile(r'''^(?:[-+]?(?:[0-9][0-9_]*)\.[0-9_]*(?:[eE][-+][0-9]+)?
-                    |\.[0-9][0-9_]*(?:[eE][-+][0-9]+)?
+        re.compile(r'''^(?:[-+]?(?:[0-9][0-9_]*)\.[0-9_]*(?:[eE][-+]?[0-9]+)?
+                    |\.[0-9][0-9_]*(?:[eE][-+]?[0-9]+)?
                     |[-+]?[0-9][0-9_]*(?::[0-5]?[0-9])+\.[0-9_]*
                     |[-+]?\.(?:inf|Inf|INF)
                     |\.(?:nan|NaN|NAN))$''', re.X),