diff --git a/project/Core/Src/tftp.c b/project/Core/Src/tftp.c
index e50ee3a..8d085bd 100644
--- a/project/Core/Src/tftp.c
+++ b/project/Core/Src/tftp.c
@@ -16,7 +16,7 @@ static tftp_custom_file_t virt_file[] =
         {.name = "virtImage.raw",.data = NULL, .len = 0, .ofset = 0}
     };
 
-int str_cat_str(char* dest, int dest_size, const char* src) {
+int str_cat_str(char* dest, size_t dest_size, const char* src) {
     int dest_len = strlen(dest);
     int src_len = strlen(src);
     if (dest_len + src_len > dest_size) {
@@ -26,7 +26,7 @@ int str_cat_str(char* dest, int dest_size, const char* src) {
     return 0;
 }
 
-int str_cat(char* dest, int dest_size, char c)
+int str_cat(char* dest, size_t dest_size, char c)
 {
     int dest_len = strlen(dest);
     if (dest_len + 1 > dest_size) {