diff --git a/src/MESA_jump_layer.cpp b/src/MESA_jump_layer.cpp
index f91f1c0..c24a4f0 100644
--- a/src/MESA_jump_layer.cpp
+++ b/src/MESA_jump_layer.cpp
@@ -211,7 +211,11 @@ static int __mjl_gtp_calc_gtp_hdr_len(const struct gtp_hdr *gtph)
 	  return -1; 
 	}
 
-	if(gtph->len > 1460)
+	if(gtph->msg_type != 0xFF){
+	  return -1;
+	}
+
+	if(ntohs(gtph->len) > 1460 || ntohs(gtph->len) < 40)
 	{
 		return -1;
 	}