diff --git a/lib/include/openamp/rpmsg_rpc_client_server.h b/lib/include/openamp/rpmsg_rpc_client_server.h
index a344cde..0d32974 100644
--- a/lib/include/openamp/rpmsg_rpc_client_server.h
+++ b/lib/include/openamp/rpmsg_rpc_client_server.h
@@ -176,7 +176,8 @@ int rpmsg_rpc_server_init(struct rpmsg_rpc_svr *rpcs, struct rpmsg_device *rdev,
  *				data
  * @param rpc_id		Function id
  * @param request_param		Pointer to request buffer
- * @param req_param_size	Length of the request data
+ * @param req_param_size	Length of the request data; must not exceed
+ *				MAX_BUF_LEN - MAX_FUNC_ID_LEN
  *
  * @return Length of the received response, negative value for failure.
  */
diff --git a/lib/service/rpmsg/rpc/rpmsg_rpc_client.c b/lib/service/rpmsg/rpc/rpmsg_rpc_client.c
index e5cb1ef..94af6f1 100644
--- a/lib/service/rpmsg/rpc/rpmsg_rpc_client.c
+++ b/lib/service/rpmsg/rpc/rpmsg_rpc_client.c
@@ -53,12 +53,16 @@ int rpmsg_rpc_client_send(struct rpmsg_rpc_clt *rpc,
 {
 	unsigned char tmpbuf[MAX_BUF_LEN];
 
-	if (!rpc)
+	if (!rpc || (!request_param && req_param_size != 0))
+		return -EINVAL;
+	/* Reserve space for the function ID before copying parameters. */
+	if (req_param_size > MAX_BUF_LEN - MAX_FUNC_ID_LEN)
 		return -EINVAL;
 
 	/* to optimize with the zero copy API */
 	memcpy(tmpbuf, &rpc_id, MAX_FUNC_ID_LEN);
-	memcpy(&tmpbuf[MAX_FUNC_ID_LEN], request_param, req_param_size);
+	if (req_param_size != 0)
+		memcpy(&tmpbuf[MAX_FUNC_ID_LEN], request_param, req_param_size);
 	return rpmsg_send(&rpc->ept, tmpbuf, MAX_FUNC_ID_LEN + req_param_size);
 }