diff --git a/app/src/main/jni/netguard/tcp.c b/app/src/main/jni/netguard/tcp.c
index 4fbbbedd..56c8d201 100644
--- a/app/src/main/jni/netguard/tcp.c
+++ b/app/src/main/jni/netguard/tcp.c
@@ -167,8 +167,11 @@ int monitor_tcp_session(const struct arguments *args, struct ng_session *s, int
 }
 
 uint32_t get_send_window(const struct tcp_session *cur) {
-    uint32_t behind = (compare_u32(cur->acked, cur->local_seq) <= 0
-                       ? cur->local_seq - cur->acked : cur->acked);
+    uint32_t behind;
+    if (cur->acked <= cur->local_seq)
+        behind = (cur->local_seq - cur->acked);
+    else
+        behind = (0x10000 + cur->local_seq - cur->acked);
     uint32_t window = (behind < cur->send_window ? cur->send_window - behind : 0);
     return window;
 }