diff --git a/pandas/core/window.py b/pandas/core/window.py
index 76ba76b7a9da9..5d2fa16876c11 100644
--- a/pandas/core/window.py
+++ b/pandas/core/window.py
@@ -1286,7 +1286,7 @@ class Expanding(_Rolling_and_Expanding):
 
     Parameters
     ----------
-    min_periods : int, default None
+    min_periods : int, default 1
         Minimum number of observations in window required to have a value
         (otherwise result is NA).
     center : boolean, default False