diff --git a/mlcolvar/cvs/committor/committor.py b/mlcolvar/cvs/committor/committor.py
index 4a672f28..bba62370 100644
--- a/mlcolvar/cvs/committor/committor.py
+++ b/mlcolvar/cvs/committor/committor.py
@@ -3,6 +3,7 @@
 from mlcolvar.cvs import BaseCV
 from mlcolvar.core import FeedForward
 from mlcolvar.core.loss import CommittorLoss
+from mlcolvar.core.nn.utils import Custom_Sigmoid
 
 __all__ = ["Committor"]
 
@@ -31,7 +32,7 @@ class Committor(BaseCV, lightning.LightningModule):
         Utils to initialize the masses tensor for the training
     """
 
-    BLOCKS = ["nn"]
+    BLOCKS = ["nn", "sigmoid"]
 
     def __init__(
         self, 
@@ -79,23 +80,16 @@ def __init__(
         # ======= OPTIONS =======
         # parse and sanitize
         options = self.parse_options(options)
-        
-        # add the relevant nn options, set tanh for hidden layers and sharp sigmoid for output layer
-        activ_list = ["tanh" for i in range( len(layers) - 2 )]
-        activ_list.append("custom_sigmoid")
-        
-        # update options dict for activations if not already set
-        if not "activation" in options["nn"]:
-            options["nn"]["activation"] = activ_list
-
-        # ======= CHECKS =======
-        # should be empty in this case
-
 
         # ======= BLOCKS =======
-        # initialize NN turning on last layer activation
+        # initialize NN turning
         o = "nn"
-        self.nn = FeedForward(layers, last_layer_activation=True, **options[o])
+        self.nn = FeedForward(layers, **options[o])
+
+        # separately add sigmoid activation on last layer, this way it can be deactived
+        o = "sigmoid"
+        if (options[o] is not False) and (options[o] is not None):
+            self.sigmoid = Custom_Sigmoid(**options[o])
 
 
     def training_step(self, train_batch, batch_idx):
@@ -153,5 +147,7 @@ def test_committor():
     trainer = lightning.Trainer(max_epochs=5, logger=None, enable_checkpointing=False, limit_val_batches=0, num_sanity_val_steps=0)
     trainer.fit(model, datamodule)
 
+    model(X).sum().backward()
+
 if __name__ == "__main__":
     test_committor()
\ No newline at end of file