diff --git a/lvgl_helpers.h b/lvgl_helpers.h
index 0e427d7..3e7715b 100644
--- a/lvgl_helpers.h
+++ b/lvgl_helpers.h
@@ -64,7 +64,7 @@ extern "C" {
 #elif defined CONFIG_LV_TFT_DISPLAY_CONTROLLER_ILI9341
 #define DISP_BUF_SIZE  (LV_HOR_RES_MAX * 40)
 #elif defined CONFIG_LV_TFT_DISPLAY_CONTROLLER_SSD1306
-#if defined (CONFIG_LV_THEME_MONO)
+#if defined (CONFIG_LV_USE_THEME_MONO)
 #define DISP_BUF_SIZE  (LV_HOR_RES_MAX * (LV_VER_RES_MAX / 8))
 #else
 #define DISP_BUF_SIZE  (LV_HOR_RES_MAX * LV_VER_RES_MAX)