diff --git a/project/Core/Src/tcp_cmd.c b/project/Core/Src/tcp_cmd.c
index 52a57ea..22beeb3 100644
--- a/project/Core/Src/tcp_cmd.c
+++ b/project/Core/Src/tcp_cmd.c
@@ -338,7 +338,7 @@ static void tcp_cmd_list_files(struct tcp_pcb* pcb, int argc, char** argv) {
  * @param[in] argv The arguments
  */
 static void tcp_cmd_set_image(struct tcp_pcb* pcb, int argc, char** argv) {
-    char* ext = NULL;
+    const char* ext = NULL;
     if (argc >= 1) {
         ext = llfs_get_filename_ext(argv[0]);
         if (strcmp(ext, "bmp") != 0) {
@@ -371,7 +371,7 @@ static void tcp_cmd_set_image(struct tcp_pcb* pcb, int argc, char** argv) {
  * @param[in] argv The arguments
  */
 static void tcp_cmd_set_gif(struct tcp_pcb* pcb, int argc, char** argv) {
-    char* ext = NULL;
+    const char* ext = NULL;
     if (argc >= 1) {
         ext = llfs_get_filename_ext(argv[0]);
         if (strcmp(ext, "gif") != 0) {