diff --git a/lib/decode.c b/lib/decode.c
index aa80acc..1b9e333 100644
--- a/lib/decode.c
+++ b/lib/decode.c
@@ -790,12 +790,18 @@ static quirc_decode_error_t decode_kanji(struct quirc_data *data,
 
 	for (i = 0; i < count; i++) {
 		int d = take_bits(ds, 13);
+		int msB = d / 0xc0;
+		int lsB = d % 0xc0;
+		int intermediate = (msB << 8) | lsB;
 		uint16_t sjw;
 
-		if (d + 0x8140 >= 0x9ffc)
-			sjw = d + 0x8140;
-		else
-			sjw = d + 0xc140;
+		if (intermediate + 0x8140 <= 0x9ffc) {
+			/* bytes are in the range 0x8140 to 0x9FFC */
+			sjw = intermediate + 0x8140;
+		} else {
+			/* bytes are in the range 0x8140 to 0x9FFC */
+			sjw = intermediate + 0xc140;
+		}
 
 		data->payload[data->payload_len++] = sjw >> 8;
 		data->payload[data->payload_len++] = sjw & 0xff;