diff --git a/pandas/core/groupby/groupby.py b/pandas/core/groupby/groupby.py
index 497e0ef724373..c73a2d40a33e1 100644
--- a/pandas/core/groupby/groupby.py
+++ b/pandas/core/groupby/groupby.py
@@ -399,7 +399,7 @@ class providing the base-class of operations.
 
 Parameters
 ----------
-f : function
+f : function, str
     Function to apply to each group. See the Notes section below for requirements.
 
     Can also accept a Numba JIT function with