diff --git a/moldocker/fitness/target.py b/moldocker/fitness/target.py
index 16ae86c..07aad7b 100644
--- a/moldocker/fitness/target.py
+++ b/moldocker/fitness/target.py
@@ -10,7 +10,7 @@
 class TargetFitness(Fitness):
     """Fitness function that optimizes a target property"""
 
-    def __init__(self, target=TARGET, tolerance=TOLERANCE):
+    def __init__(self, target=TARGET, tolerance=TOLERANCE, **kwargs):
         """
         Args:
             target (float): target value for the property
diff --git a/moldocker/samplers/voronoi.py b/moldocker/samplers/voronoi.py
index c5d322d..731fa01 100644
--- a/moldocker/samplers/voronoi.py
+++ b/moldocker/samplers/voronoi.py
@@ -15,7 +15,7 @@
 
 PROBE_RADIUS = 0.1
 MIN_VORONOI_RADIUS = 3.0
-REMOVE_SPECIES = ["O"]
+REMOVE_SPECIES = []
 NUM_CLUSTERS = 10