diff --git a/rowers/dataprep.py b/rowers/dataprep.py
index ea252e89..a03c01ee 100644
--- a/rowers/dataprep.py
+++ b/rowers/dataprep.py
@@ -363,7 +363,7 @@ def save_workout_database(f2,r,dosmooth=True,workouttype='rower',
         velo = 500./pace
                 
         f = row.df['TimeStamp (sec)'].diff().mean()
-        if f !=0:
+        if f !=0 and not np.isnan(f):
             windowsize = 2*(int(10./(f)))+1
         else:
             windowsize = 1