diff --git a/include/proto/proto_tcp.h b/include/proto/proto_tcp.h
index 0712764..4644452 100644
--- a/include/proto/proto_tcp.h
+++ b/include/proto/proto_tcp.h
@@ -64,7 +64,7 @@
  */
 static inline int tcp_trk_idx(int trk_action)
 {
-	return trk_action - TCP_ACT_TRK_SC1;
+	return trk_action - TCP_ACT_TRK_SC0;
 }
 
 #endif /* _PROTO_PROTO_TCP_H */