diff --git a/python/fbprophet/forecaster.py b/python/fbprophet/forecaster.py
index 7fbd67b..973728c 100644
--- a/python/fbprophet/forecaster.py
+++ b/python/fbprophet/forecaster.py
@@ -896,7 +896,7 @@ class Prophet(object):
         first = self.history['ds'].min()
         last = self.history['ds'].max()
         dt = self.history['ds'].diff()
-        min_dt = dt.iloc[dt.values.nonzero()[0]].min()
+        min_dt = dt.iloc[dt.to_numpy().nonzero()[0]].min()
 
         # Yearly seasonality
         yearly_disable = last - first < pd.Timedelta(days=730)