diff --git a/lifelines/fitters/cox_time_varying_fitter.py b/lifelines/fitters/cox_time_varying_fitter.py
index cb48f7925..d58cb4112 100644
--- a/lifelines/fitters/cox_time_varying_fitter.py
+++ b/lifelines/fitters/cox_time_varying_fitter.py
@@ -801,7 +801,7 @@ def _compute_cumulative_baseline_hazard(self, tv_data, events, start, stop, weig
             hazards = self.predict_partial_hazard(tv_data).values
 
         unique_death_times = np.unique(stop[events.values])
-        baseline_hazard_ = pd.DataFrame(np.zeros_like(unique_death_times), index=unique_death_times, columns=["baseline hazard"])
+        baseline_hazard_ = pd.DataFrame(np.zeros_like(unique_death_times).astype(float), index=unique_death_times, columns=["baseline hazard"])
 
         for t in unique_death_times:
             ix = (start.values < t) & (t <= stop.values)