diff --git a/src/packet_interface.h b/src/packet_interface.h
index 181dc94a21d823b623621c5a7de5645da6d627d9..7428389f7a4a349822d67d0219452cdd56a060d1 100644
--- a/src/packet_interface.h
+++ b/src/packet_interface.h
@@ -68,7 +68,7 @@ typedef enum {
 #define TR_MASK                         0x20
 #define WINDOW_MASK                     0x1F
 #define TR_SETTER_TO_ZERO               0xDF
-#define SECOND_TO_LAST_PKT              0xFFFFFFFF // Use to specify it was the second to last pkt sent by the sender
+#define SECOND_TO_LAST_PKT              0x3AB33922 // Use to specify it was the second to last pkt sent by the sender -> Need to be random ?
 
 #define TYPE_SHIFT                      6
 #define TR_SHIFT                        5
diff --git a/src/sender.c b/src/sender.c
index 4b81e0a5a21becac84af61a118334c20ace08322..017f8256bb0f0d8f79fddd5676553e8c9ea4a621 100644
--- a/src/sender.c
+++ b/src/sender.c
@@ -156,7 +156,8 @@ int main(int argc, char **argv) {
         }
         else if (can_send(state) && (pfd->revents & POLLOUT))
         {
-            DEBUG("The sender will send a pkt on the socket, the current sender window size is: %d", state->s_window_size);
+            DEBUG("The sender will send a pkt on the socket, the current sender window size is: %d | receiver window size: %d", 
+            state->s_window_size, state->r_window_size);
             rvalue = read_and_send(state, sending_fd, socket_fd);
             if (rvalue == -1)
             {
diff --git a/src/sender_utils.c b/src/sender_utils.c
index bdcdea1edb7aaeaf009d39ab96ca7b4525fa61b1..27aed81460f8ad466bae7434d40fdf85d27e4cae 100644
--- a/src/sender_utils.c
+++ b/src/sender_utils.c
@@ -146,8 +146,8 @@ int handle_returning_ack_nack(sender_state_t *state, int socket_fd)
             }
             else
             {
-                DEBUG("The receiver is asking AGAIN, the seqnum: %d", seqnum_nack);
-                state->r_window_size = r_window;
+                DEBUG("The receiver is asking AGAIN, the seqnum: %d so the sender sends it back", seqnum_nack);
+                state->r_window_size = r_window - 1; // -1 Because the receiver doesn't count yet the sended pkt
                 pkt_t *n_pkt = state->buffer[place_last_nack];
                 if (send_pkt(state, n_pkt, place_last_nack, socket_fd) == -1) return -1;
                 return 0;