diff --git a/sys/dev/powermac_nvram/powermac_nvram.c b/sys/dev/powermac_nvram/powermac_nvram.c
index 7c6c4d2bc8a..bce511463d3 100644
--- a/sys/dev/powermac_nvram/powermac_nvram.c
+++ b/sys/dev/powermac_nvram/powermac_nvram.c
@@ -362,7 +362,7 @@ adler_checksum(uint8_t *data, int len)
 	high = 0;
 	for (i = 0; i < len; i++) {
 		if ((i % 5000) == 0) {
-			high %= 65521UL;
+			low %= 65521UL;
 			high %= 65521UL;
 		}
 		low += data[i];