diff --git a/majortrack/tracker.py b/majortrack/tracker.py
index 09bed94..96d9911 100644
--- a/majortrack/tracker.py
+++ b/majortrack/tracker.py
@@ -2510,7 +2510,10 @@ def include_cluster(idx, group):
                     )
             prev_idx = idx
         self.sp_clusters = {
-                _clusters_x_pos[idx]: _clusters[idx]
+                _clusters_x_pos[idx]: [
+                    cluster for cluster in _clusters[idx]
+                    if cluster is not None
+                    ]
                 for idx in range(len(_clusters))
                 }
         self.sp_fluxes = {