diff --git a/rdtools/soiling.py b/rdtools/soiling.py
index 554f06b8..8d1e7b47 100644
--- a/rdtools/soiling.py
+++ b/rdtools/soiling.py
@@ -341,8 +341,8 @@ def _calc_result_df(self, trim=False, max_relative_slope_error=500.0, max_negati
                 "run_slope_high": 0,
                 "max_neg_step": min(run.delta),
                 "start_loss": 1,
-                "inferred_start_loss": run.pi_norm.median(),  # changed from mean/Matt
-                "inferred_end_loss": run.pi_norm.median(),  # changed from mean/Matt
+                "inferred_start_loss": np.nan if run.pi_norm.isna().any() else run.pi_norm.median(),  # changed from mean/Matt
+                "inferred_end_loss": np.nan if run.pi_norm.isna().any() else run.pi_norm.median(),  # changed from mean/Matt
                 "slope_err": 10000,  # added high dummy start value for later logic/Matt
                 "valid": False,
                 "clean_event": run.clean_event.iloc[0],  # record of clean events to distiguisih