diff --git a/Doc/library/platform.rst b/Doc/library/platform.rst
index a71d533..36275ed 100644
--- a/Doc/library/platform.rst
+++ b/Doc/library/platform.rst
@@ -104,7 +104,7 @@
 .. function:: python_implementation()
 
    Returns a string identifying the Python implementation. Possible return values
-   are: 'CPython', 'IronPython', 'Jython'.
+   are: 'CPython', 'IronPython', 'Jython', 'PyPy'.
 
 
 .. function:: python_revision()