diff --git a/backend/rss.c b/backend/rss.c
index 2eb3aac1..af0a323e 100644
--- a/backend/rss.c
+++ b/backend/rss.c
@@ -1982,7 +1982,7 @@ int rssexpanded(struct zint_symbol *symbol, unsigned char source[], int src_len)
 	   elements in the data characters. */
 	checksum = 0;
 	for(i = 0; i < data_chars; i++) {
-		row = weight_rows[(((data_chars - 3) / 2) * 21) + i];
+		row = weight_rows[(((data_chars - 2) / 2) * 21) + i];
 		for(j = 0; j < 8; j++) {
 			checksum += (char_widths[i][j] * checksum_weight_exp[(row * 8) + j]);
 			
diff --git a/backend/rss.h b/backend/rss.h
index 2da7a046..f1463a9b 100644
--- a/backend/rss.h
+++ b/backend/rss.h
@@ -173,7 +173,7 @@ static int checksum_weight_exp[184] = { /* Table 14 */
 	76, 17, 51, 153, 37, 111, 122, 155,
 	43, 129, 176, 106, 107, 110, 119, 146,
 	16, 48, 144, 10, 30, 90, 59, 177,
-	109, 166, 137, 200, 178, 112, 125, 164,
+	109, 116, 137, 200, 178, 112, 125, 164,
 	70, 210, 208, 202, 184, 130, 179, 115,
 	134, 191, 151, 31, 93, 68, 204, 190,
 	148, 22, 66, 198, 172, 94, 71, 2,