Mention version in which the new marshal version was introduced.
diff --git a/Doc/c-api/marshal.rst b/Doc/c-api/marshal.rst
index c075495..4df6288 100644
--- a/Doc/c-api/marshal.rst
+++ b/Doc/c-api/marshal.rst
@@ -14,7 +14,8 @@
The module supports two versions of the data format: version 0 is the historical
version, version 1 (new in Python 2.4) shares interned strings in the file, and
-upon unmarshalling. Version 2 uses a binary format for floating point numbers.
+upon unmarshalling. Version 2 (new in Python 2.5) uses a binary format for
+floating point numbers.
*Py_MARSHAL_VERSION* indicates the current file format (currently 2).