diff --git a/project/Core/Src/mqtt_application.c b/project/Core/Src/mqtt_application.c
index 4ecaea8..21c0a3e 100644
--- a/project/Core/Src/mqtt_application.c
+++ b/project/Core/Src/mqtt_application.c
@@ -160,7 +160,7 @@ static void mqtt_incoming_data_cb(void* arg, const uint8_t* data, uint16_t len,
             LOG_INFO(TAG, "incoming data on input/setImage: %s.", data_buffer);
             lcd_clear_images();
             lcd_set_bg_color_layer0(bgcolor);
-            if (strlen(data_buffer) >= 3) {
+            if (len >= 3) {
                 if (data_buffer[len - 3] == 'b') {
                     lcd_draw_img_from_fs((const char*)data_buffer, xpos, ypos);
                 }