diff --git a/src/config/defaults/efi.h b/src/config/defaults/efi.h
index ed7d37f26..4c9ba9d2a 100644
--- a/src/config/defaults/efi.h
+++ b/src/config/defaults/efi.h
@@ -28,7 +28,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define FDT_EFI
 #define MPAPI_EFI
 #define NAP_EFI
-#define SERIAL_FIXED
+#define SERIAL_SPCR
 
 #define	NET_PROTO_IPV6		/* IPv6 protocol */
 #define	NET_PROTO_LLDP		/* Link Layer Discovery protocol */
diff --git a/src/config/defaults/pcbios.h b/src/config/defaults/pcbios.h
index 9be9ff834..3f24f1b7b 100644
--- a/src/config/defaults/pcbios.h
+++ b/src/config/defaults/pcbios.h
@@ -26,7 +26,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define REBOOT_PCBIOS
 #define ACPI_RSDP
 #define MPAPI_PCBIOS
-#define SERIAL_FIXED
+#define SERIAL_SPCR
 
 #ifdef __x86_64__
 #define IOMAP_PAGES
diff --git a/src/config/serial.h b/src/config/serial.h
index 6dc051df4..a372963aa 100644
--- a/src/config/serial.h
+++ b/src/config/serial.h
@@ -26,6 +26,10 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define	COMSPEED	115200		/* Baud rate */
 #endif
 
+/* Uncomment these to ignore the ACPI SPCR table (if present) */
+//#undef SERIAL_SPCR
+//#define SERIAL_FIXED
+
 /* Early UART configuration (for bare metal prefix debugging only) */
 //#define EARLY_UART_MODEL	8250
 //#define EARLY_UART_REG_BASE	0x10000000