diff --git a/utils/mnettoss/mnettoss.c b/utils/mnettoss/mnettoss.c
index b53d9d2..fb87846 100644
--- a/utils/mnettoss/mnettoss.c
+++ b/utils/mnettoss/mnettoss.c
@@ -272,7 +272,7 @@ void update_config_file_area(int areaid) {
     int id;
     int i;
 
-    snprintf(backup, "%s.bak", config_file);
+    snprintf(backup, PATH_MAX, "%s.bak", config_file);
     fptr1 = fopen(config_file, "r");
     fptr2 = fopen(backup, "w");