diff --git a/pyfstat/optimal_setup_functions.py b/pyfstat/optimal_setup_functions.py
index 811dece452d85f8355f2d871580a7798a2591bd1..80a7072d57e4c25ee690573ceb999007b234e818 100644
--- a/pyfstat/optimal_setup_functions.py
+++ b/pyfstat/optimal_setup_functions.py
@@ -214,8 +214,8 @@ def get_Nstar_estimate(
             fiducial_freq, detectors, detector_weights, detector_motion,
             ephemeris)
     except RuntimeError as e:
-        logging.debug('Encountered run-time error {}'.format(e))
-        return None, None, None
+        logging.warning('Encountered run-time error {}'.format(e))
+        raise RuntimeError("Calculation of the SSkyMetric failed")
 
     if sky:
         i = 0