diff --git a/pri_facility.c b/pri_facility.c
index 291b620..284136b 100644
--- a/pri_facility.c
+++ b/pri_facility.c
@@ -42,6 +42,7 @@
 
 static short get_invokeid(struct pri *ctrl)
 {
+	ctrl = PRI_MASTER(ctrl);
 	return ++ctrl->last_invoke;
 }
 
diff --git a/pri_internal.h b/pri_internal.h
index 861cbdc..fbde7e1 100644
--- a/pri_internal.h
+++ b/pri_internal.h
@@ -138,7 +138,7 @@ struct pri {
 	unsigned int q931_rxcount;
 #endif
 
-	short last_invoke;	/* Last ROSE invoke ID */
+	short last_invoke;	/* Last ROSE invoke ID (Valid in master record only) */
 	unsigned char sendfacility;
 };