diff --git a/common/parity.h b/common/parity.h
index bceb9cf2..c574db55 100644
--- a/common/parity.h
+++ b/common/parity.h
@@ -23,7 +23,7 @@ static inline bool oddparity8(const uint8_t x) {
 }
 
 static inline void oddparitybuf(const uint8_t *x, size_t len, uint8_t *parity) {
-	memset(parity, 0x00, len / 8 + 1);
+	memset(parity, 0x00, (len - 1) / 8 + 1);
 	for (int i = 0; i < len; i++) 
 		parity[i / 8] |= oddparity8(x[i]) << (7 - (i % 8));
 }