diff --git a/src/main/scala/mupq/PQVexRiscvSim.scala b/src/main/scala/mupq/PQVexRiscvSim.scala
index 8b233dd..1d5603c 100644
--- a/src/main/scala/mupq/PQVexRiscvSim.scala
+++ b/src/main/scala/mupq/PQVexRiscvSim.scala
@@ -155,6 +155,7 @@ object PQVexRiscvSim {
 
       val uartTxd = dut.io.uart.txd
       val uartRxd = dut.io.uart.rxd
+      uartRxd #= true
 
       val uartDecoder = fork {
         sleep(1)