diff --git a/model_custom.py b/model_custom.py
index acc83b01b846b38de9c45d14c5142b9b045b87d2..30fb32f7afd4832db668662524039bfd9a9e2db7 100644
--- a/model_custom.py
+++ b/model_custom.py
@@ -39,7 +39,7 @@ class PositionalEncoding(nn.Module):
 
 class Model_Common_Transformer(nn.Module):
 
-    def __init__(self, drop_rate=0.1, embedding_dim=128, nb_aa=24,
+    def __init__(self, drop_rate=0.1, embedding_dim=128, nb_aa=23,
                  regressor_layer_size_rt=512, regressor_layer_size_int=512, decoder_rt_ff=512, decoder_int_ff=512,
                  n_head=1, seq_length=25,
                  charge_max=4, charge_frag_max=3, encoder_ff=512, encoder_num_layer=1, decoder_rt_num_layer=1,