diff --git a/zipline/pipeline/factors/factor.py b/zipline/pipeline/factors/factor.py
index 2e6463b3..b75192a3 100644
--- a/zipline/pipeline/factors/factor.py
+++ b/zipline/pipeline/factors/factor.py
@@ -617,9 +617,9 @@ class CustomFactor(PositiveWindowLengthMixin, CustomTermMixin, Factor):
         argument is passed to the CustomFactor constructor, we look for a
         class-level attribute named `inputs`.
     window_length : int, optional
-        Number of rows of rows to pass for each input.  If this
-        argument is not passed to the CustomFactor constructor, we look for a
-        class-level attribute named `window_length`.
+        Number of rows to pass for each input.  If this argument is not passed
+        to the CustomFactor constructor, we look for a class-level attribute
+        named `window_length`.
 
     Notes
     -----