diff --git a/arch/sim/src/sim/sim_usrsock.c b/arch/sim/src/sim/sim_usrsock.c
index fd7b66d922875..f297ae3aa7795 100644
--- a/arch/sim/src/sim/sim_usrsock.c
+++ b/arch/sim/src/sim/sim_usrsock.c
@@ -78,6 +78,7 @@ static int usrsock_send_ack(struct usrsock_s *usrsock,
 
   ack.head.msgid = USRSOCK_MESSAGE_RESPONSE_ACK;
   ack.head.flags = (result == -EINPROGRESS);
+  ack.head.events = 0;
 
   ack.xid    = xid;
   ack.result = result;
@@ -93,6 +94,7 @@ static int usrsock_send_dack(struct usrsock_s *usrsock,
 {
   ack->reqack.head.msgid = USRSOCK_MESSAGE_RESPONSE_DATA_ACK;
   ack->reqack.head.flags = 0;
+  ack->reqack.head.events = 0;
 
   ack->reqack.xid    = xid;
   ack->reqack.result = result;