diff --git a/pygam/terms.py b/pygam/terms.py
index a2ec3ed4..57157e65 100644
--- a/pygam/terms.py
+++ b/pygam/terms.py
@@ -638,6 +638,10 @@ def __init__(self, feature, n_splines=20, spline_order=3, lam=0.6,
             in the case that `spline_basis="cp"`, `edge_knots` determines
             the period of the cyclic function.
 
+            when `edge_knots=None` these values are inferred from the data.
+
+            default: None
+
         by : int, optional
             Feature to use as a by-variable in the term.