diff --git a/Marlin/src/lcd/marlinui.cpp b/Marlin/src/lcd/marlinui.cpp
index 1e25021..c40f7a9 100644
--- a/Marlin/src/lcd/marlinui.cpp
+++ b/Marlin/src/lcd/marlinui.cpp
@@ -198,8 +198,13 @@ constexpr uint8_t epps = ENCODER_PULSES_PER_STEP;
       WRITE(LCD_BACKLIGHT_PIN, HIGH);
     #endif
   }
+#elif ENABLED(PROUI_EX)
+  void MarlinUI::refresh_backlight_timeout() {
+    // do nothing
+  }
+#endif
 
-#elif HAS_DISPLAY_SLEEP
+#if HAS_DISPLAY_SLEEP
 
   constexpr uint8_t MarlinUI::sleep_timeout_min, MarlinUI::sleep_timeout_max;
 
diff --git a/Marlin/src/lcd/marlinui.h b/Marlin/src/lcd/marlinui.h
index 8b077f3..5e8f128 100644
--- a/Marlin/src/lcd/marlinui.h
+++ b/Marlin/src/lcd/marlinui.h
@@ -278,7 +278,11 @@ public:
     static uint8_t backlight_timeout_minutes;
     static millis_t backlight_off_ms;
     static void refresh_backlight_timeout();
-  #elif HAS_DISPLAY_SLEEP
+  #elif ENABLED(PROUI_EX)
+    static void refresh_backlight_timeout();
+  #endif
+
+  #if HAS_DISPLAY_SLEEP
     static constexpr uint8_t sleep_timeout_min = 0;
     static constexpr uint8_t sleep_timeout_max = 99;
     static uint8_t sleep_timeout_minutes;