diff --git a/rogueviz/som/kohonen.h b/rogueviz/som/kohonen.h
index 0feda5e5..20fb3693 100644
--- a/rogueviz/som/kohonen.h
+++ b/rogueviz/som/kohonen.h
@@ -63,6 +63,8 @@ extern vector<string> colnames;
 
 extern vector<int> sample_sequence;
 
+extern vector<neuron*> whowon;
+
 void initialize_neurons();
 void initialize_neurons_initial();
 void initialize_dispersion();