diff --git a/pycbc/types/timeseries.py b/pycbc/types/timeseries.py
index 3bf94065473..70d8802cb23 100644
--- a/pycbc/types/timeseries.py
+++ b/pycbc/types/timeseries.py
@@ -188,10 +188,10 @@ def time_slice(self, start, end, mode='floor'):
         start_idx = float(start - self.start_time) * self.sample_rate
         end_idx = float(end - self.start_time) * self.sample_rate
 
-        if _numpy.isclose(start_idx, round(start_idx)):
+        if _numpy.isclose(start_idx, round(start_idx), rtol=0, atol=1E-3):
             start_idx = round(start_idx)
 
-        if _numpy.isclose(end_idx, round(end_idx)):
+        if _numpy.isclose(end_idx, round(end_idx), rtol=0, atol=1E-3):
             end_idx = round(end_idx)
 
         if mode == 'floor':