diff --git a/project/Core/Src/UDP_broadcast.c b/project/Core/Src/UDP_broadcast.c
index 413801e..70b29e3 100644
--- a/project/Core/Src/UDP_broadcast.c
+++ b/project/Core/Src/UDP_broadcast.c
@@ -97,7 +97,7 @@ static void format_reply(owner_details_t *owner){
 	char mac_addr_str[18];
 	char* reply_buf = NULL;
 	if (owner != NULL) {
-		reply_len = 20 + strlen(mac_addr_str) + strlen(owner->surname) + strlen(owner->name);
+		reply_len = 20 + sizeof(mac_addr_str) + sizeof(owner->surname) + sizeof(owner->name);
         reply_buf = (char*)malloc(reply_len);