diff --git a/repos/base-sel4/patches/serial.patch b/repos/base-sel4/patches/serial.patch
new file mode 100644
index 000000000..627dc757e
--- /dev/null
+++ b/repos/base-sel4/patches/serial.patch
@@ -0,0 +1,24 @@
+--- src/kernel/sel4/src/plat/pc99/machine/io.c
++++ src/kernel/sel4/src/plat/pc99/machine/io.c
+@@ -18,7 +18,7 @@
+ 
+ void serial_init(uint16_t port)
+ {
+-    while (!(in8(port + 5) & 0x60)); /* wait until not busy */
++    while (!(in8(port + 5) & 0x20)); /* wait until not busy */
+ 
+     out8(port + 1, 0x00); /* disable generating interrupts */
+     out8(port + 3, 0x80); /* line control register: command: set divisor */
+@@ -43,10 +43,10 @@ void console_putchar(char c)
+     lock_acquire(&lock_debug);
+ 
+     if (port > 0) {
+-        while (!(in8(port + 5) & 0x60));
++        while (!(in8(port + 5) & 0x20));
+         out8(port, c);
+         if (c == '\n') {
+-            while (!(in8(port + 5) & 0x60));
++            while (!(in8(port + 5) & 0x20));
+             out8(port, '\r');
+         }
+     }
diff --git a/repos/base-sel4/ports/sel4.hash b/repos/base-sel4/ports/sel4.hash
index e45ae0f42..2d137115c 100644
--- a/repos/base-sel4/ports/sel4.hash
+++ b/repos/base-sel4/ports/sel4.hash
@@ -1 +1 @@
-2b60b5d96865ba4f4d362a80729af31305d13a31
+e8d740ed612452a8d81b992169f459191b3a3f0c