diff --git a/libpri.h b/libpri.h
index b7fd5bf..675a097 100755
--- a/libpri.h
+++ b/libpri.h
@@ -545,6 +545,7 @@ extern void pri_enslave(struct pri *master, struct pri *slave);
 #define PRI_SETUP_CALL
 #define PRI_RECEIVE_SUBADDR
 #define PRI_REDIRECTING_REASON
+#define PRI_AOC_UNITS
 
 /* Send notification */
 extern int pri_notify(struct pri *pri, q931_call *c, int channel, int info);