diff --git a/figures/beacon/src/beacon_field.py b/figures/beacon/src/beacon_field.py
index 523bbc1..1970f22 100755
--- a/figures/beacon/src/beacon_field.py
+++ b/figures/beacon/src/beacon_field.py
@@ -184,7 +184,7 @@ if __name__ == "__main__":
     command_group.add_argument('--time',  help='Use the time difference for the field', action='store_false')
     command_group.add_argument('--phase', help='Use wrapped phase for the field', action='store_true')
 
-    parser.add_argument('--ref', dest='ref_ant', metavar='ref_antenna', help='Number of antenna to use as reference')
+    parser.add_argument('--ref', dest='ref_ant', metavar='ref_antenna', type=int, help='Number of antenna to use as reference')
 
     args = parser.parse_args()
 
@@ -248,7 +248,10 @@ if __name__ == "__main__":
     ### Options
     ###
     plot_phase = args.plot_phase
-    ref_ant = args.ref_ant
+    if args.ref_ant:
+        ref_ant = ants[args.ref_ant]
+    else:
+        ref_ant = None
 
 
     ant_combi = antenna_combinations(ants, ref_ant=ref_ant)