Fix markup.
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index d8e7d44..9bccf5d 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -300,7 +300,7 @@
    platform and libm implementation. It's usually :exc:`ValueError` for *EDOM*
    and :exc:`OverflowError` for errno *ERANGE*.
 
-   ..versionchanged:: 2.6
+   .. versionchanged:: 2.6
       In earlier versions of Python the outcome of an operation with NaN as
       input depended on platform and libm implementation.