diff --git a/tests/test_serial.c b/tests/test_serial.c
index 9691037..a7c3752 100644
--- a/tests/test_serial.c
+++ b/tests/test_serial.c
@@ -34,6 +34,8 @@
 
 	rc = write(ctx->egress, buf, len);
 	assert(rc == len);
+
+	return rc;
 }
 
 uint8_t mctp_msg_src[2 * MCTP_BTU];