diff --git a/pycbc/detector.py b/pycbc/detector.py
index f9b42da7465..155f692e12e 100644
--- a/pycbc/detector.py
+++ b/pycbc/detector.py
@@ -697,8 +697,10 @@ def __init__(self, detector='LISA', reference_time=None, orbits=ESAOrbits(), use
         
         # specify and cache the start time and orbital time series
         if reference_time is None:
-            reference_time = self.orbits.t_base[0]
-        self.ref_time = reference_time
+            ref_time = self.orbits.t_base[0]
+        else:
+            ref_time = reference_time
+        self.ref_time = ref_time
         self.sample_times = None
 
         # cache the FLR instance along with dt and n