diff --git a/wolfcrypt/src/kdf.c b/wolfcrypt/src/kdf.c
index 3b452d56f..34514e49b 100644
--- a/wolfcrypt/src/kdf.c
+++ b/wolfcrypt/src/kdf.c
@@ -910,7 +910,7 @@ static void wc_srtp_kdf_first_block(const byte* salt, word32 saltSz, int kdrIdx,
         }
         else {
             /* XOR in as bit shifted index. */
-            block[WC_SRTP_MAX_SALT - indexSz] ^= index[i+0] >> bits;
+            block[WC_SRTP_MAX_SALT - indexSz] ^= index[0] >> bits;
             for (i = 1; i < indexSz; i++) {
                 block[i + WC_SRTP_MAX_SALT - indexSz] ^=
                     (index[i-1] << (8 - bits)) |