diff --git a/Src/CanSerialPortFrameTP.c b/Src/CanSerialPortFrameTP.c
index c63e757..41d20e0 100644
--- a/Src/CanSerialPortFrameTP.c
+++ b/Src/CanSerialPortFrameTP.c
@@ -202,8 +202,8 @@ bool sendFirstFrame(tCanSerialPortFrameTp *env, uint8_t *data, uint16_t size, ui
         pDataLen += 7;
 
         ++sn;
-        if (sn == 15) {
-            sn = 1;
+        if (sn > 15) {
+            sn = 0;
         }
     }