diff --git a/Thalamic_Column.h b/Thalamic_Column.h
index 1d8e885..4caa70d 100644
--- a/Thalamic_Column.h
+++ b/Thalamic_Column.h
@@ -214,7 +214,7 @@ class Thalamic_Column {
                         m_h2	= init(0.0);	/* activation 	of h   channel bound with protein 	*/
 
     /* Data storage  access */
-    friend void get_data (unsigned, Thalamic_Column&, std::vector<double*>);
+    friend void get_data (unsigned, Thalamic_Column&, std::vector<double*>&);
 };
 /****************************************************************************************************/
 /*										 		end			 										*/