--- a/netwerk/srtp/src/crypto/replay/rdbx.c
+++ b/netwerk/srtp/src/crypto/replay/rdbx.c
@@ -137,25 +137,25 @@ int32_t srtp_index_guess(const srtp_xtd_
     uint32_t guess_roc = (uint32_t)(*guess >> 16);
     uint16_t guess_seq = (uint16_t)*guess;
 #endif
     int32_t difference;
 
     if (local_seq < seq_num_median) {
         if (s - local_seq > seq_num_median) {
             guess_roc = local_roc - 1;
-            difference = s - local_seq - seq_num_max;
+            difference = seq_num_max - s + local_seq;
         } else {
             guess_roc = local_roc;
             difference = s - local_seq;
         }
     } else {
         if (local_seq - seq_num_median > s) {
             guess_roc = local_roc + 1;
-            difference = s - local_seq + seq_num_max;
+            difference = seq_num_max - local_seq + s;
         } else {
             guess_roc = local_roc;
             difference = s - local_seq;
         }
     }
     guess_seq = s;
 
 /* Note: guess_roc is 32 bits, so this generates a 48-bit result! */