diff --git a/src/pc80/mc146818rtc.c b/src/pc80/mc146818rtc.c
index 034957acf5..99d670de42 100644
--- a/src/pc80/mc146818rtc.c
+++ b/src/pc80/mc146818rtc.c
@@ -1,3 +1,4 @@
+#include <stdint.h>
 #include <console/console.h>
 #include <pc80/mc146818rtc.h>
 #include <boot/coreboot_tables.h>
@@ -80,12 +81,11 @@
 static int rtc_checksum_valid(int range_start, int range_end, int cks_loc)
 {
 	int i;
-	unsigned sum, old_sum;
+	u16 sum, old_sum;
 	sum = 0;
 	for(i = range_start; i <= range_end; i++) {
 		sum += cmos_read(i);
 	}
-	sum = (~sum)&0x0ffff;
 	old_sum = ((cmos_read(cks_loc)<<8) | cmos_read(cks_loc+1))&0x0ffff;
 	return sum == old_sum;
 }
@@ -93,7 +93,7 @@ static int rtc_checksum_valid(int range_start, int range_end, int cks_loc)
 static void rtc_set_checksum(int range_start, int range_end, int cks_loc)
 {
 	int i;
-	unsigned sum;
+	u16 sum;
 	sum = 0;
 	for(i = range_start; i <= range_end; i++) {
 		sum += cmos_read(i);
diff --git a/src/pc80/mc146818rtc_early.c b/src/pc80/mc146818rtc_early.c
index abddf87661..0652f27c47 100644
--- a/src/pc80/mc146818rtc_early.c
+++ b/src/pc80/mc146818rtc_early.c
@@ -1,3 +1,4 @@
+#include <stdint.h>
 #include <pc80/mc146818rtc.h>
 #include <fallback.h>
 #if CONFIG_USE_OPTION_TABLE
@@ -23,13 +24,12 @@ static int cmos_chksum_valid(void)
 {
 #if CONFIG_USE_OPTION_TABLE
 	unsigned char addr;
-	unsigned long sum, old_sum;
+	u16 sum, old_sum;
 	sum = 0;
-	/* Comput the cmos checksum */
+	/* Compute the cmos checksum */
 	for(addr = LB_CKS_RANGE_START; addr <= LB_CKS_RANGE_END; addr++) {
 		sum += cmos_read(addr);
 	}
-	sum = (sum & 0xffff) ^ 0xffff;
 
 	/* Read the stored checksum */
 	old_sum = cmos_read(LB_CKS_LOC) << 8;