diff --git a/Doc/library/cmath.rst b/Doc/library/cmath.rst
index f04f8d01955..85393dca8a2 100644
--- a/Doc/library/cmath.rst
+++ b/Doc/library/cmath.rst
@@ -257,6 +257,8 @@ Constants
 
    The mathematical constant *τ*, as a float.
 
+   .. versionadded:: 3.6
+
 .. index:: module: math
 
 Note that the selection of functions is similar, but not identical, to that in
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index 32e1352bfff..da2b8cc5862 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -434,6 +434,8 @@ Constants
    Wrong <https://www.youtube.com/watch?v=jG7vhMMXagQ>`_, and start celebrating
    `Tau day <http://tauday.com/>`_ by eating twice as much pie!
 
+   .. versionadded:: 3.6
+
 .. data:: inf
 
    A floating-point positive infinity.  (For negative infinity, use