diff --git a/nfapi/open-nFAPI/pnf/src/pnf_p7.c b/nfapi/open-nFAPI/pnf/src/pnf_p7.c
index 27b59870089c5b036b6c203b183af29c4103b303..5efcf9d7cc73631b2998eb9c548c798ac97d9a07 100644
--- a/nfapi/open-nFAPI/pnf/src/pnf_p7.c
+++ b/nfapi/open-nFAPI/pnf/src/pnf_p7.c
@@ -36,7 +36,7 @@ extern uint16_t sf_ahead;
 
 void add_sf(uint16_t *frameP, uint16_t *subframeP, int offset)
 {
-    *frameP    = *frameP + ((*subframeP + offset) / 10);
+    *frameP    = (*frameP + ((*subframeP + offset) / 10))%1024;
 
     *subframeP = ((*subframeP + offset) % 10);
 }