diff --git a/src/serial.s b/src/serial.s
index c2dd6ea..b7b07a4 100644
--- a/src/serial.s
+++ b/src/serial.s
@@ -28,7 +28,7 @@ INITUART
   stb UART_DLL  ; Write divisor LSB
   puls b
   stb UART_LCR  ; Write LCR
-  lda UARTF_FCR_FE|UARTF_FCR_RFR|UARTF_FCR_XFR ; FIFO disable and clear
+  lda #(UARTF_FCR_FE|UARTF_FCR_RFR|UARTF_FCR_XFR) ; FIFO disable and clear
   sta UART_FCR
   lda #0
   sta UART_IER  ; Polled mode