diff --git a/arch/powerpc/kernel/udbg_16550.c b/arch/powerpc/kernel/udbg_16550.c
index e58c048..7541bf4 100644
--- a/arch/powerpc/kernel/udbg_16550.c
+++ b/arch/powerpc/kernel/udbg_16550.c
@@ -137,7 +137,7 @@
 	speed = (clock / prescaler) / (divisor * 16);
 
 	/* sanity check */
-	if (speed < 9600 || speed > 115200)
+	if (speed < 0 || speed > (clock / 16))
 		speed = 9600;
 
 	return speed;